THE LARYNX OF MAN TODAY

The Structure

As explained by Johannes Sobotta,⁴ the laryngeal framework consists of three cartilages—the epiglottis, the thyroid cartilage, and the cricoid cartilage (Fig. 17)—held together by ligaments, muscles, and joints. The thin, leafshaped cartilage, the epiglottis (Fig. 17), is attached to the thyroid cartilage by means of the thyroepiglottic ligament (Fig. 19). It is attached to the inferior surface of the anterior part of the thyroid cartilage just above the origin of the vocal folds (Figs. 17 and 19). The thyroid cartilage (Figs. 17-19) is shield-shaped and is the most prominent of the laryngeal framework. Supporting the thyroid is the cricoid cartilage (Figs. 17 and 18), which is ring-shaped and higher in the back than in the front. The cricoid and the thyroid are articulated with a movable joint at the point of the inferior cornu and the arch of the cricoid (Figs. 17-19). The arytenoids (Figs. 17 and 19), two tiny pyramid-shaped cartilages with triangular bases, are seated on the posterior prominence of the cricoid cartilage and furnish the posterior attachment for the vocal folds (Fig. 19).

Fig. 17. Cartilages of the Larynx (after Sobotta)

Ligaments and Membranes

The ligaments and membranes of the larynx in man today are as follows:

1. Hyothyroid ligament—Connects the hyoid bone and the thyroid cartilage, and extends from cornu of hyoid downward to cornu of thyroid (Fig. 18).

Fig. 18. Ligaments and Membranes, Anterior

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

Fig. 19. Ligments and Membranes, Posterior

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

2. Cricotracheal ligament—Connects the cricoid cartilage and the trachea (Fig. 18).

3. Thyroepiglottic ligament—Connects the epiglottis and the thyroid cartilage (Fig. 19).

4. Cricothyroid ligament (medial)—Connects the cricoid and the thyroid cartilage at their anterior position (Fig. 18).

5. Ceratocricoid ligament (lateral)—Connects the cricoid and the thyroid cartilage at the inferior cornu and the posterior surface of the cricoid (Figs. 18-19).

6. Ceratocricoid ligament (posterior)—Connects the cricoid and the thyroid cartilage at the inferior cornu and the posterior surface of the cricoid (Fig. 19).

7. Cricoarytenoid ligament—Connects the arytenoids and the cricoid cartilage (Fig. 19).

8. Corniculate pharyngeal ligament—Connects corniculate cartilage with the cricoid cartilage at the pharyngeal wall (Fig. 19).

9. Vocal ligaments—Paired thickened stripes of elastic cone that originate at the inner surface of the angle of the thyroid cartilage and extend posteriorly to the vocal process of each arytenoid cartilage (Fig. 20).

10. Aryepiglottic fold—These membranes follow, even to the individual folds, the contour of the skeleton of the larynx and its ligaments (Figs. 21-22). From the epiglottis (Figs. 21-22), the two aryepiglottic folds pass backward to the tips of the corniculate cartilages and forms the lateral boundaries of the vestibule. In addition, the corniculate cartilages and the cuneiform cartilages (Figs. 21-22) are contained within the posterior-superior surface of the fold. They are identified as knob-like elevations in the surface of the membrane. Their function is to draw the opening of the vestibule together.

11. Conus elasticus and cricothyroid membrane—The conus elasticus (Fig. 20) is a short cone-shaped tube which hangs like a tough curtain between the thyroid and the arytenoid cartilages. It is the framework upon which the muscular function of the vocal folds is based. The cone form leans forward so that the tip of the cone is attached to the lower border of the thyroid cartilage at its median raphe. As the sides of the cone drape downward they spread and form a circle at the base of the cone; this circle is attached to the upper surface of the cricoid cartilage (Fig. 20). The conus is slit along its upper edge, and the upper borders of the slit form the vocal ligament (Fig. 20). The posterior and superior portion of the slits are attached to the base of the vocal process of each arytenoid. The arytenoids in their gliding articulations open and close the slit (the glottis). The anterior portion of the cone forms the cricothyroid membrane. The conus elasticus is covered with muscle and tissue, which are loosely attached to it. As the thyroarytenoid muscle contracts the conus becomes firm. It has three points of attachment. The lower border of the thyroid cartilage, the upper surface of the cricoid cartilage, and the inferior surface of the vocal process of each arytenoid.

Fig. 20. Conus Elasticus

Above the vocal fold is the laryngopharynx or the vestibule (Fig. 21). It is bordered anteriorly by the epiglottis, posteriorly by the arytenoid cartilages and laterally by a membrane (the aryepiglottic folds), which forms a wall between the epiglottis and the arytenoids (Figs. 21A-21C). The false vocal folds or ventricular folds are formed from the lower part of this membrane (Figs. 21A and 21B). These folds are part muscle and part ligament, and they spread out above and parallel to the vocal folds. The space between the vocal and the false vocal folds is called the ventricle of Morgagni (Figs. 21A and 21B). Fig. 21C displays the laryngopharynx and its position in the foodway. Since the cartilaginous framework of the larynx is completely covered by membranous tissue from the tip of the epiglottis to its continuation with the trachea, the laryngopharynx is a closed resonating system. The lower pharyngeal area (piriform sinus) is part of the foodway which surrounds the laryngopharynx, laterally and posteriorly, permitting it to be suspended, almost freely, in the foodway during phonation. The contour of the laryngopharynx is altered during the production of vowels. (See Fig. 41.) Not only is the orifice altered, but its transverse and vertical aspects also are altered.

Fig. 21A. Laryngopharynx (Vestibule), Section, Lateral View

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

Fig. 21B. Laryngopharynx, Section, Posterior View

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

Fig. 21C. Position of the Laryngopharynx in the Foodway

(after Sobotta)

MUSCULATURE AND MECHANICS OF PHONATION

A method of instruction which relates a specific muscle structure to a specific respiratory or phonatory act is bound to be seriously defective and oversimplified. All disciplined vocal utterance in song is derived through the unification of numerous muscle complexes that are interrelated and form a huge gestalt. The performer recognizes these unified actions as a single sensation.

However, one must realize that specific laryngeal muscles cause the arytenoid cartilages to slide or revolve, which in turn approximate the vocal folds and close the glottis in preparation for the act of phonation. Six of these muscles, three of them paired, are prime movers and can be used to explain the mechanics of phonation. They are known as the intraarytenoid muscles. They consist of the transverse, oblique, posterior, lateral cricoarytenoid, cricothyroid, and thyroarytenoid.

Fig. 22A. Muscles of the Larynx, Lateral View

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

Transverse Arytenoids

Origin—Posterior surface and outer border of each arytenoid (Figs. 23A and 23B).

Insertion—Outer border of each arytenoid.

Action—Draws together the arytenoid cartilages, closes glottis respiratoria (between arytenoids).

Fig. 22B. Muscles of the Larynx, Posterior View

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

Fig. 23A, Transverse Arytenoids, Origin and Insertion B, Transverse Arytenoids, Action

Fig. 24A, Oblique Arytenoids, Origin and Insertion B, Oblique Arytenoids, Action

Oblique Arytenoids (Figs. 24A and 24B)

Origin—Base of posterior surface of one arytenoid.

Insertion-Apex of posterior surface of opposite cartilage. Fibers of each muscle cross to form an X.

Action—Stabilizes the arytenoids by drawing tips of arytenoids together and aids in closing the glottis.

Posterior Cricoarytenoids (Figs. 25A and 25B)

Origin—Posterior surface of the cricoid cartilage.

Insertion—Muscular process of each arytenoid.

Action—Rotates vocal process of arytenoid cartilage outward so that the vocal processes are drawn away from the midline. Opens the glottis vocalis.

Fig. 25A, Posterior Cricoarytenoids, Origin and Insertion B, Posterior Cricoarytenoids, Action

These muscles tilt the arytenoid backward with consequent rise of the vocal process and the tensing of the vocal ligament.

Lateral Cricoarytenoids (Figs. 26A and 26B)

Origin—Upper border and side of each cricoid cartilage.

Insertion—Muscular process of each arytenoid.

Action—Pulls the arytenoid cartilage forward, and when opposed by the action of the posterior cricoarytenoids, creates a state of suspended tension in the vocal ligament. This action rotates the arytenoids and moves the vocal processes inward, and thus closes the glottis vocalis.

Cricothyroid (Fig. 27A)

Origin—Oblique fibers, anterior border of the cricoid cartilage.

Insertion—Lower lamina and inferior cornu of the thyroid.

Action—By drawing the inferior cornu forward these fibers tilt the cricoid cartilage upward. This action approximates and lengthens the vocal folds rendering them tense in preparation for phonation (Fig. 27B).

Origin—Anterior fibers. Front and superior superior surface of the cricoid cartilage.

Insertion—Anterior border and lower lamina of the thyroid cartilage (Fig. 27A).

Action—Depresses the thyroid cartilage and elevates the arch of the cricoid cartilage, or draws the thyroid forward and downward. This combined action increases the distance between the vocal processes of the arytenoid and the lamina of the thyroid. It elongates the vocal folds and renders them tense, provided the arytenoids remain fixed. This downward tilt is effected by the singer to give stability to the phonated sound and to permit him to increase intensity as the pitch is maintained. The pitch is also raised by stretching the vocal folds. The degree of the thyroid tilt affects pitch, intensity, and quality of the vocal sound (Fig. 27C).

Fig. 27A. Cricothyroid, Orgin and Insertion

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

Fig. 27B. Cricothyroid, Action

Fig. 27C. Cricothyroid, Action

Thyroarytenoid

This muscle is divided into two parts, the vocalis muscle and the external thyroarytenoid.

Vocalis Muscle. (Figs. 28A and 28B)

Origin—The angle of the thyroid cartilage.

Insertion—The vocal process of the arytenoid cartilage.

External Thyroarytenoid. (Figs. 28A and 28B)

Origin—The angle of the thyroid cartilage.

Insertion—The base and anterior surface of the arytenoid cartilage.

Laterally, it is attached to the wall of the thyroid cartilage.

Fibers of the vocalis muscle are nearest the vocal ligament and are attached to its inferior and lateral surface. Fibers of the external thyroarytenoid interdigitate with the fibers of the vocalis muscle and are attached laterally and anteriorly to the inner wall of the thyroid cartilage.

These two segments of muscle run parallel to each other with points of insertion indicated above. However, some of the fibers of the vocalis muscle are short and do not extend to the vocal process of each arytenoid cartilage. These fibers, attached to the vocal ligament and conus elasticus (Fig. 20), perform the refined tasks of controlling the conformation of the vocal fold in its various states of thickness and thinness during changes of pitch.

When the vocal folds are not approximated, as in the absence of phonation, a space is created between them called the rima glottidis or glottis. During passive breathing the glottic opening extends from the thyroid cartilage to the posterior border of the arytenoids. Its anterior-posterior length in the male is approximately twenty-four millimeters, and in the female approximately fifteen millimeters.

Fig. 28A. Thyroarytenoid, Origin and Insertion, Superior View

(after Sobotta)

That portion of the glottis extending from the thyroid cartilage to the tip of the vocal process of the arytenoid is known as the glottis vocalis. That portion of the glottis which lies between the arytenoid cartilages is known as the glottis respiratoria (Fig. 28A). Chronic breathiness in the vocalized sound is sometimes caused by a failure of the arytenoids to approximate, thereby permitting the glottis respiratoria to remain open.

Fig. 28B. Thyroarytenoid, Posterior Section of the Left Fold

Source: Reproduced from A. Mayet, “Bau und funktion des musculus vocalis und seine Beziehungen zer lig. vocale und conus elasticus,” Acta Anatomica, Vol. 24 (1955), 15-25. Hamalaun-Eosin, illustrator. Basel (Switz.), and New York: S. Karger.

Action—The independent action of these thyroarytenoid muscles may:

1. Relax and shorten the vocal ligament by drawing the arytenoids towards the thyroid cartilage for the singing of low pitches (Fig. 29A).

2. Draw the vocal processes of the arytenoids downward and inward, approximating the vocal folds (Fig. 29B).

Fig. 29A. Thyroarytenoid, Action, Lateral View

Fig. 29B. Thyroarytenoid, Action, Superior View

3. Pull the vocal folds apart by their lateral contraction.

4. Become stabilized throughout their entire length and, thereby, aid in raising the pitch of the phonated sound.

5. Vary both the length and thickness of the vibrating segment.

6. Render a portion of the vocal fold tense while the remainder is relaxed. Thus, an elliptical opening between the vocal folds is maintained for the production of higher pitches.

Such control of the glottic opening results from the action of certain fibers of the vocalis muscle that are fastened to the border of the vocal ligament. They are able to pull apart against the tension of a portion of or the entire length of each fold, in order to establish the final pattern in which the vibration will take place. Pressman suggests physiological reasons for such an elliptical opening based upon the arrangement of fibers in the vocalis muscle described by Piersol.⁵

Fig. 30. Suggested Arrangement of Fibers in the Vocalis Muscle

Source: Joel J. Pressman, “Physiology of the Vocal Cords in Phonation and Respiration,” Archives of Otolaryngology, Vol. 35 (1942).

1. Fibers arising anteriorly in the thyroid cartilage and passing posteriorly more or less parallel to the general direction of the cords,^* to terminate at different levels [Fig. 30A]. The innermost fibers are very short and terminate in the anterior portion of the cords. The more lateral fibers are longer, inserting farther and farther posteriorly until the most lateral ones extend from the anterior point of origin on the thyroid cartilage to the posterior extremity of the cords near the arytenoids or into the vocal processes themselves.

2. Fibers arising at various points within the substance of the vocal cord and conus elasticus (of which the former is a part) and passing backward to insert on the body and vocal process of the arytenoid cartilages [Fig. 30B].

3. Fibers arising here and there in the substance of the cords and extending backward for varied distances to insert on the same cord at a more posterior point [Fig. 30C].

Fig. 31. Adduction of the Vocal Folds Causes a Rise in Pitch by Contraction of the Fibers of Vocalis Muscle

Source: Joel J. Pressman, “Physiology of the Vocal Cords in Phonation and Respiration,” Archives of Otolaryngology, Vol. 35 (1942).

None of these three groups can be recognized as an entity, since a great deal of intertwining of the fibers of each group with those of the others takes place.

The action of these groups of fibers is on the cord and is probably as varied as the arrangement of the fibers is complex. Their most important action in phonation seems to take place after the cords have been strongly and completely approximated and tensed by the adductor group. When this tension and adduction have been accomplished, it then becomes necessary to reopen the cords by some means which permits them to retain their relatively rigid elasticity. The action of these internal fibers of the thyroarytenoideus muscle is admirably suited for the purpose. Starting with the arytenoids tightly closed and the vocal bands on stretch and closely adherent, those internal fibers of the thyroarytenoidei which arise on the thyroid cartilage and insert into the cordal structure contract. They thus pull apart, against the tension of the adductors, those portions of the vocal cords into which they insert [Fig. 31]. This action takes place in much the manner that an archer draws back the tense bowstring of his bow, the arm of the archer representing the muscle fibers of the thyroarytenoideus muscle and the taut bowstring representing the tensed vocal cord. When the pull of these fibers is released, the cord returns sharply to the midline, corresponding to the release of the bowstring by the archer. The length of the cord pulled apart is determined by the number of fibers of this portion of the thyroarytenoideus muscle which are called into play. The variation in the length of cord pulled apart is important from the standpoint of variations in pitch.

Those fibers of the thyroarytenoideus muscle arising in the vocal process of the arytenoid and extending forwward to be inserted into the cord at different points have the same action, supplementing that just described, except that the pull comes from a posterior instead of an anterior point. The chief reason for believing that there are such fibers is that if a segment of the cord is to be bowed laterally, as actually occurs, instead of anterolaterally, a compensatory group of fibers must exert a posterior pull against the action of any group that might arise anteriorly.

The fibers arising in one portion of a cord and inserting in another further supplement this action and give the margins of the glottis increased elasticity and rigidity.⁶

The numerous possibilities of action of the thyroarytenoids depend upon the action of the other laryngeal muscles (posterior cricoarytenoids, lateral cricoarytenoids, and the cricothyroid) which act as guying muscles during the complex act of phonation. If these muscles are not balanced correctly one with the other as antagonists, an imbalance occurs within the system, and this imbalance is evident in the vocal utterance in such effects as breathiness caused by improper closure of the glottic aperture or faulty pitch caused by an imbalance between the actions of the posterior cricoarytenoids and the thyroarytenoids. When the posterior cricoarytenoids are weak, the thyroarytenoids become much too tense in attempting to hold the pitch constant. Lack of range often results from insufficient tension within the thyroarytenoid. Tension within the vocal folds is coordinated with the contraction of the cricothyroid muscle (Fig. 27B); the resulting tilt of the thyroid tenses the vocalis muscle for thoracic fixation or phonation.

THEORIES OF LARYNGEAL VIBRATION

In considering the physical principles of laryngeal vibration, the scientist is faced with several basic facts that are either physiological or physical in nature. All theorists have accepted these facts; however, they differ in their analyses of the mechanism which controls the refined movements of the thyroarytenoid muscles in the production of pitch and of various tone qualities.

Husson⁷ and his coworkers have produced the neurochronaxic theory that motor impulses from the central nervous system cause rhythmic contractions of the thyroarytenoid muscles producing the vibrations requisite for any given tone. However, as pointed out by Negus and others,⁸ tones as high as 2,048 cycles per second have been recorded by the human voice, but tonic contractions of the thyroarytenoid muscle may occur with stimuli only to 110 cycles per second. Therefore, the thyroarytenoid cannot function clonically on all pitches.

Because of these objections, contemporary researchers favor an aerodynamic theory in which air flow and cavity resonances seem to affect frequency and intensity rather than direct muscular and neural controls.

Two theories will be considered, the reed theory and the vibrating string theory.

Contemporary vocal theorists accept the following as facts:

1. That all vocalized sound is the result of expiration of air through the coneshaped narrowing of the phonatory tube at the apex of the trachea (Fig. 21B).

2. That further constriction is applied by the vocal folds which are capable of completely or partially interrupting the expired air.

3. That both the vocal folds and walls of the airway are elastic and yield under pressure (Figs. 44-46).

4. That the vocal folds are capable of varying in length, tension, and contour—thereby regulating the size, shape, and the position of the glottic aperture—as well as undergoing vibrating movements.

5. That the laryngeal muscles do not produce the vocal sound. Rather, phonation is an aerodynamic phenomenon in which the muscles merely adjust and hold the folds in a certain position, tension, and shape. The modulation of the expired air stream, caused by the movement of the vibrating vocal folds, makes the sound. The resulting pressure variations create the multiple sine waves which comprise the complex vocal spectrum.

The Larynx as an Air-Column Instrument—
The Reed Theory

For many years teachers have described the action of the vocal folds as analogous to the vibrating reeds of the oboe. According to the reed theory, changes in pitch are caused (a) by changing the contour of the glottic aperture, (b) by altering the elasticity of the margins of the folds, and (c) by varying the contour of the total resonating system.

According to Jackson and Schatz,⁹ tone production and pitch variation at the larynx are analogous to a mechanism in which the reeds come together momentarily and more or less close off the expired air. They then open and allow the air to escape in puffs. This process repeated rapidly represents the vibration of the already approximated vocal folds; it is not to be confused with simple abduction (separation) or adduction (bringing together). In this manner the air stream is cut off periodically by the approximation of the folds. This rapid escape of air is what produces the sound. At this point the reed theory seems to be sound, for the expanded air does escape in puffs. Evidence that rapid escape of air in puffs will produce sound is found in the function of a siren which consists of a circular metal plate perforated around its margin. A jet of air directed toward the holes while the plate rotates rapidly will produce an intense sound. The intervals between the small apertures represent the opening and the closing of the reed or vocal fold. An increase in the velocity of the wheel’s rotation causes a rise in pitch.

According to the reed theory, the vocal folds vary the pitch in much the same way that pitch is changed by the lips of a bugler, that is, by enlarging or diminishing the size of the orifice, by varying its firmness and shape, and by changing the force of the expired air. Jackson¹⁰ says that the total resonating system is involved in pitch change, an area extending from the labial orifice to the bifurcation of the trachea into the two bronchi; that with each rise in pitch, both supraglottic and infraglottic air columns are decreased, vertically and transversely, two to three millimeters.

Because this action does occur, at first it seems to support the reed theory for it involves the principle of forced vibration. (See p. 117, No. 1.) Those who advance this theory assume that the vibrator is dominated by the resonator which causes the vibrator, or reed, to vibrate in the period of the system as the system changes its contour and dimension in the production of vocalized sound. The defenders of this theory believe that a total system or gestalt is involved in which both laryngeal musculature and phonatory airway contribute to changes in pitch and vocal quality.

A closer examination of the laws of forced vibration reveal the fallacy of the reed theory: The conception of a reed or air-column instrument fails because the principle of instrumental design is to make the frequency of the instrument dependent, not upon the natural frequency of the reed, but upon the natural frequency of the air column to which it is coupled.

When making lip slurs on the trumpet, the reverse of this principle is true, the vibrator dominates the resonator and the slur is accomplished by moving a perfect fifth upward or downward by lip tension and increased breath pressure alone. Slurs on reed instruments are accomplished in a similar manner. The clarinet has a natural interval of the twelfth, but in both cases it is the domination of the vibrator over the resonator that effects the smooth transition from one frequency to another.

Changes of pitch in singing arise, at least in part, from the variation in length, tension, and mass of the vocal folds. In this case, the vibrator dominates the resonator, compelling the resonator to respond to a frequency related to the vibrator regardless of the natural frequency of the resonator.

The Vibrating-String Theory

Each string of a stringed instrument is tuned to specific pitches, which are determined by the tension, length, mass, and elasticity of the string. The greater the tension the higher the pitch of the resulting sound when the string is plucked or bowed. If the tension is doubled, the pitch will rise one octave. A short string will produce a higher pitch than a long string; the pitch will rise one octave if the string length is halved.

The thickness or mass of a string affects both pitch and timbre. If the mass of the string is decreased the pitch rises, and if the mass is increased, the pitch lowers because of greater inertia created by the additional mass.

The mass of a string depends upon its elasticity. In a flexible elastic material, less inertia is produced and a greater mass may be employed before the limit of its tension is reached.

Therefore, a note of the same pitch can be produced with string of varying length, tension, mass, and elasticity provided the ratios between these elements are correct. The tone quality will vary in each case; this variation accounts for the differences between instruments of the same type, particularly between two different makes of violins.

This principle of vibrating strings also confirms the variation between singers of the same tessitura, type, or class in that each will vary his application of amplitude, mass, length, and tension while producing the same pitch.

The vibrating-string theory precludes that the vocal folds are able to produce tones just as they are produced upon the violin, the force of expired air provides the energy by which the tone is made at the larynx.

This theory also includes the concept that pitch may be varied in the larynx by increasing the tension of the vocal folds just as pitch is elevated by tightening the violin string.

The tension of any vibrating string is controlled by its elasticity. Elevation of the pitch can be carried to a limited point by this process of elongation or tightening.

The action of the thyroarytenoid in singing an ascending scale is illustrated in the Bell Telephone pictures. They show that in the production of the lowest note of the scale the glottis is open widest in its posterior part, nearest the arytenoid cartilages, and that the vocal folds are short and thick. As this pitch is sung, the laryngeal muscles are under the least tension and the amplitude of the vibrations are most extreme. The lateral movement of the folds extend through the entire thyroarytenoid. The folds are loose and flaccid (Fig. 32).

Fig. 32. Pitch Change

Action of the vocal folds during changes of pitch in the middle voice shows alterations of mass, length, and tension of the folds. A is at b, 123; B at b, 246; and C at e, 329. Source: Bell Telephone Laboratories, Inc.

As the pitch rises, the cricothyroid muscles tense and tilt the thyroid cartilage so that the vocal folds gradually become longer, thinner, and more tense. Here the amplitude of the vibration decreases as the tension of the fold increases. This increase in tension is created by the action of the inner fibers of the vocalis muscle, the lateral cricoarytenoid, the posterior arytenoids, and the cricothyroid muscles. This added tension causes the amplitude of the vibrations to decrease and the glottic aperture to narrow gradually until the opening becomes linear in shape (Fig. 33). At this point the vocal folds are vibrating at their full length. This mode of vibration is characteristic of the middle register before adduction.

Fig. 33. Position of the Vocal Folds in the Production of Middle Tones

The enlarged posterior hiatus has disappeared, the margins of the vocal folds now parallel one another. Variations in the length and tension of the folds and in their degree of approximation produce with this same pattern variations of pitch within reasonable limits. Source: Joel J. Pressman, “Physiology of the Vocal Cords in Phonation and Respiration,” Archives of Otolaryngology Vol. 35 (1942).

The tension upon the thyroarytenoid muscle continues to increase, but the elasticity of the folds is not sufficient to permit further stretching. At this point further elevation of the pitch is achieved in a manner similar to fingering a violin. In singing, this functional foreshortening is achieved by the approximation of a portion of the vocal folds against each other, beginning posteriorly (Fig. 34). The segments in contact with each other are not able to vibrate so that each contacting segment is said to be in the state of adduction. This pressing together of the posterior portion of the vocal folds permits the remaining shorter segment to vibrate, and a corresponding elevation of the pitch is produced. As greater lengths of the vocal folds come in contact with each other, the glottic aperture becomes smaller. The reduction in the size of the glottis further tends to elevate the pitch according to the acoustic principles of air passing through a smaller orifice. This elliptically shaped glottis is achieved by the contraction of the inner fibers of the vocalis muscle and by the strong guying action of the total laryngeal musculature. (Fig. 31). To reiterate, vocal sound starts with the modulation of tracheal air flow resulting from the vibrations of the glottic margins. The frequency (and the resulting pitch) of the sound is varied by changes in the elasticity of the glottal margins and the length which is free to vibrate, these changes are controlled by the thyroarytenoid and associated musculature.

Fig. 34. Position of Vocal Folds in the Production of Higher Tones

In A the folds are in the first stage of adduction. In B adduction of the folds has shortened the length of each fold which is free to vibrate, raising the pitch of the sung sound. In C the segments free to vibrate are very short, and the tone produced is very high. Source: Joel J. Pressman, “Physiology of the Vocal Cords in Phonation and Respiration,” Archives of Otolaryngology, Vol. 35 (1942).

This act conforms with the law of vibrating strings except that the vocal folds grow longer from the lower to the middle tones instead of shorter. However, at this point the mass of the folds decreases (They become thinner as the pitch rises.); further elevation of the pitch is brought about by an increase of tension and refined controls of the total laryngeal musculature.

The larynx of man as a biosocial organ has no exact functional counterpart in man-made instruments, and teaching techniques must be built around conceptual differences in tonal control but with complete insight and an awareness of the physiological and the psychological phenomena involved in each vocal act.

SYNTHESIS OF ACTION IN PHONATION FOR SINGING

Action of Body Musculature

Phonation for singing is produced by the laryngeal generator. The body’s muscular action begins with inspiration:^*

1. The thoracic musculature is set.

2. The pelvic diaphragm contracts, supporting the viscera (coccygeus levatores ani).

3. Abdominal diaphragm contracts, lowering the floor of the thorax and compressing the viscera. Other muscles involved are serratus superior, serratus inferior, quadratus lumborum, pectoralis major, pectoralis minor, and latissimus dorsi.

4. These actions increase the anterior-posterior vertical diameter of the thorax and the upper part of the abdomen, widen the intercostal spaces, and thus permit air to rush in.

The muscular action of expiration is sphincteric (closing a circle). Compression of the viscera is instantaneous and equal from all musculature.

1. The muscles of the abdominal wall contract: transverse thoracic, rectus abdominus, transverse abdominus, internal oblique, and external oblique.

2. The pelvic diaphragm contracts. Active contraction of these muscles dominates the holding action of the diaphragm and thereby elevates the abdominal viscera, pushes the domes of the diaphragm into the thoracic cavity, and decreases the volume of the cavity and also of the lung.

Action of Laryngeal Musculature

1. Arytenoids are approximated, closing the glottis respiratoria; the muscles involved are the posterior, oblique, and transverse arytenoids.

2. Vocal processes are rotated and meet at midline closing the glottis vocalis; the muscle involved is the lateral cricoarytenoid.

3. Arytenoid cartilages are fixed on their facets; muscles involved are the cricoarytenoid, posterior, and lateral.

4. Elasticity of the fold is increased. Muscular action involves cricothyroid, cricoarytenoids, and thyroarytenoids.

5. As the elasticity of the folds increases, breath pressure forces the vocal folds to rise and separate in a rippled wave that begins deep in the laryngeal fibers of the thyroarytenoids. This wave moves upward¹¹ as well as anteriorly from the arytenoids to the epiglottis; as the breath passes through the conical trachea and expands into the broader vestibule, it causes reduced lateral pressure upon the vocal folds. This reduced pressure creates a sucking effect (Bernoulli effect, Fig. 35), which, with the elasticity of the vocal folds, draws them together and the entire process is repeated.

Fig. 35. Bernoulli Effect in Singing

The modulation of the respiratory air stream creates the audible laryngeal “buzz” as it passes through the glottis. The complex sound waves (not sinusoidal—see p. 121) thus emitted are the result of pressure variations of the escaping bursts or puffs of air and not the result of the mechanical vibration of the folds themselves.

Pitch changes, then, are not directly attributed to a single act of lengthening, thinning, tightening, or loosening of the vocal folds. Rather, the pitch change is caused by the modulation of tracheal air pressure resulting from the changes in the elasticity of the glottal margins. It is thus assumed that the changes in the elasticity are caused by changes in mass, length, and tension of the thyroarytenoid in a synchronized act, a most complicated process. In summary, three wave-like movements of the vocal lips occur during phonation:

1. A horizontal displacement along the glottis takes place during the opening phase as noted in the Bell Telephone high-speed motion pictures of the human vocal cords. The glottis opens anterior-posteriorly and closes posterior-anteriorly (Fig. 36A). Svend Smith describes the variation between the Bell subject and his own subject as follows (Fig. 36B):

Fig. 36A. A Comparison of Vocal Fold Vibration

Source: upper photographs, Bell Telephone Laboratories, Inc.; lower photographs, Svend Smith, “Remarks on the Physiology of the Vibration of the Vocal Cords,” Folio Phoniatrica, 6 (1954), 196-271. Published by S. Karger, Basel (Switz.) and New York.

Fig. 36B. A Comparison of Vocal Fold Vibration

Source: upper photographs, Bell Telephone Laboratories, Inc.; lower photographs, Svend Smith.

Fig. 37. Vertical and Lateral Movement of the Folds

Source: Svend Smith, “Remarks on the Physiology of the Vibration of the Vocal Cords,” Folio Phoniatrica, Vol. 6 (1954), 196-271. Published by S. Karger, Basel (Switz.) and New York.

Several pictures in the Bell film reveal a bottle-like opening as the next phase after the initial front explosion. This means that the arytenoid region is the last to be opened. Of course this is only the case when the interarytenoid and lateral muscles work in a fully normal manner. In the case of a slight insufficiency [of breath]—as could most often be expected in a subject during laryngoscopy—both the front and rear part of the glottis may open simultaneously [my subject]. This would presumably cause a less violent explosion of air giving in its turn fewer overtones in the voice production [less glottic shock].¹²

The vocal folds can open anterior-posteriorly as well as posterior-anteriorly depending upon the nature of the attack and upon the coordination between the total laryngeal musculature and the breath pressure.

2. A vertical movement of the cords begins from underneath the opening and progresses upward and outward.

3. The third wave-like movement is a movement of the medial planes surrounding an air bubble. In viewing the schema, one must remember that the vocal folds are in a rolling motion, moving in these pictures posterior-anteriorly, from the bottom of each picture to the top (Fig. 37).

Smith describes the action in the following manner:

After the explosion (i.e., release of pressure) a stream of air follows. The velocity of air—together with some lateral pressure of the [external thyroarytenoid] vocal muscles—tends to suck the two medial planes against one another. The edges would not be the first portion of the vocal lips to be sucked, because they are in an excursion phase, being thrown out laterally and upwards. But the subglottic parts of the vocal lips are free to be sucked. According to the law of Bernoulli the planes now meet, not in their whole length at the same time, but gradually and well down in the subglottic region. The descending movement of the lips would support this subglottic phase of adduction.¹³

THE ANATOMY OF THE HUMAN RESONATING SYSTEM

A consideration of the laws of resonance within hard-walled Helmholtz resonators reveals the applicability of these same laws to the human resonating system.

Resonance in song depends upon four cavities that are stable resonators and upon the characteristics of these cavities to vary greatly in their ability to change in size, shape, aperture, and length of neck of the aperture. They are listed below with their respective volumes:

1. The nasal cavity (75 cubic centimeters).

2. The oral cavity (100 cubic centimeters).

3. The pharyngeal cavity and its subdivisions, the nasopharynx, the oropharynx and the laryngopharynx (80 cubic centimeters).

4. The trachea (35 cubic centimeters).¹⁴

The nasal cavity (Fig. 38) extends from the floor of the cranium to the roof of the oral cavity. The septum divides this large cavity into two separate cavities called fossae, which act as resonators in the production of nasal sounds. The nasal fossae are not amenable to change, and their conformation cannot be changed during phonation at any pitch or intensity. The nose has no other significant resonating cavities. This nasal cavity has two orifices, the anterior nares at the front of the nose and the posterior nares at the opening into the oropharynx. Neither of these orifices is subject to control.

The oral cavity (Fig. 38), the narrow passage from the mouth to the pharynx, extends from the pillars of the fauces to the labial orifice and is the most amenable to change. The shape and size of the oral cavity may be varied by the movement of the mandible, the tongue, and the lips. Too often the labial orifice is ignored as an important articulator in singing; many teachers seek a minimum of lip movement during the production of all vowel sounds. The professional singer, however, has learned that lip-rounding and lip protrusion when singing the rounded frontal vowels provide a stability and comfort not available when he fails to utilize the wide variety of shapes and sizes which this most flexible orifice is capable of forming.

The pharynx (Figs. 38 and 39), approximately four and one-half inches in length, extends from the base of the skull to the level of the sixth cervical vertebra. It is subdivided into three separate cavities; each contributes a quality component to the tonal spectrum by being a part of a tightly coupled system during the production of all sounds. As a resonating cavity the pharynx is relatively undamped.

The nasopharynx (Figs. 38 and 39) extends vertically from the base of the skull to the velum anterior-posteriorly from the posterior nares to the pharyngeal wall. It is a closed resonator and does not serve a primary function during the production of most vowels and consonants because the uvula is pressed firmly against the pharyngeal wall, thus closing the entrance to the nasopharynx.

The soft palate is raised and the velum is pressed against the pharyngeal wall by the action of the levator veli palatini, a muscle originating at the base of the cranium and extending to the palate and uvula.

The muscles which pull the palate away from the posterior wall of the pharynx are the palato-pharyngeus, the palatoglossus, and the tensor palati, which is antagonist to the levator veli palatini.

Fig. 38. The Human Resonation System, Lateral View

From The Ciba Collection of Medical Illustrations by Frank H. Netter, M.D. Copyright Ciba.

Fig. 39. The Pharyngeal Cavity and Vestibule

From The Ciba Collection of Medical Illustrations by Frank H. Netter, M.D. Copyright Ciba.

This movement permits the pharyngeal isthmus to remain open during the act of breathing and closed during the act of swallowing in order to prevent the passage of food into the nasal cavity.

As the uvula and soft palate are raised, they become tense and present a taut, hard surface for the reflection of sound. As the uvula and soft palate are loose and pendant, damping increases. This characteristic affects vowel quality and phonemic migration. The nasopharynx serves as a resonator in the production of the nasal continuants [n], [m], [ŋ], and when the velum is deliberately removed from the pharyngeal wall during the production of vowels.

The oropharynx (Fig. 39) extends vertically from the velum and uvula to the tip of the epiglottis. The anterior boundary is the postdorsum and the root of the tongue; the posterior border is the pharyngeal wall. The oropharynx is most amenable to change through the movement of the larynx. Its transverse dimension is altered by the action of the pharyngeal constrictor muscles and muscles of articulation.

The laryngopharynx (vestibule Fig. 39) is an important resonator in the coupled phonatory system, which will be described in this chapter. It extends from the tip of the epiglottis to the superior surface of the vocal folds, its lateral boundaries are the aryepiglottic folds which completely enfold it. Its superior orifice is the epiglottis, which covers it as a lid during the act of swallowing. The inferior orifice is the glottis. The laryngopharynx has within its musculature the ventricular folds (false vocal folds), which rise and nearly approximate during phonation. In rising they create beneath them, another potential resonating system, the ventricles of the larynx (Fig. 40). The formant contribution of the ventricles to the tonal spectrum is somewhat in doubt at this time.

Fig. 40A, Trumpet Mouthpiece and Player's Lips B, Vocal Fold and Laryngeal Ventricles

Fig. 41. Movement of the Vestibule, Anterior View

Source: D. Ralph Appelman, “Study by Means of Planigraph, Radiograph, and Spectograph of Physiological Changes During Register Transition in Vocal Tones” (Ph.D. dissertation, School of Music, Indiana University, 1953).

Musehold suggests that the ventricles and ventricular folds form a cupshaped cavity with a point of constriction at the ventricular fold approximation much the same as the fixed cavity within a trumpet mouthpiece (Fig. 40).¹⁵ This assumption is a logical one, but further research is needed for its substantiation.

Tomograms made by the author at Indiana University in 1953¹⁶ reveal the changes in the vertical and transverse conformation of the vestibule and the ventricles during the singing three vowels [i], [a], and [u], pitch f, 349 cycles per second (Fig. 41). Changes in the laryngeal position are also evident at the level of the vocal folds. The white air spaces at each side of the vestibule are the piriform sinuses, part of the foodway. They serve as an open area permitting the lateral expansion of the vestibule during phonation.

A most primary vestibular movement is evident in the variation of the position of the epiglottis during the phonation of the front and the back vowels when they are sung within the stable vowel pitch range. This anterior-posterior movement reveals changes in the vestibular opening, which alters the conformation and dimension of the vestibule during the production of each vowel (Figs. 41 and 42). During phonation this movement is controlled by movements of the tongue root anteriorly and the holding action of the thyroepiglottic and the aryepiglottic muscles.

The Trachea

The trachea (Fig. 43) is a cartilaginous membranous tube extending from the subglottic larynx to the division of the bronchi. It is approximately eleven centimeters long in men and ten centimeters long in women. The trachea has eighteen cartilages, each of which forms two-thirds of a ring. The posterior third of the circumference is made up of transverse fibers called the trachealis muscle. This muscle contracts the tracheal ring and, thereby, decreases its diameter. Relaxation of the trachealis enlarges the ring and permits the passage of large volumes of air during forced respiration.

Fig. 42. Anterior-Posterior Movement of the Epiglottis,^* Lateral View

Variation in the position of the epiglottis during the phonation of vowels in the stable vowel pitch range, reveals changes in the vestibular opening which alters the conformation and dimension of the vestibule during the production of each vowel. (See also Fig. 41.)

The trachea is an important resonator in the phonatory tube, but little empirical evidence pertains to its specific function as an infraglottic resonator in singing.

Tomograms¹⁷ reveal a tracheal alteration—a bulbous enlargement below the base of the cricoid cartilage—during the production of high pitches and increased vocal force. This condition appears in all voices. The lateral expansion is caused by infraglottic pressure, since the contraction of the trachealis muscle permits only an increase in the anterior-posterior expansion of the tracheal ring (Figs. 44-46).

Fig. 43. The Trachea

Source: Johannes Sobotta and Eduard Uhlenhuth, Human Anatomy (7th ed.; New York: Hafner Publishing Co., 1957).

The Open Throat in Singing

The open throat used in singing is the result of increasing the anterior-posterior, transverse, and vertical dimension of the oral and pharyngeal cavities from their normal positions used in the production of speech sounds. Although the movements of the postdorsum and root of the tongue are responsible for altering the size and shape of the pharyngeal cavity (See kinesiologic analysis of vowels, Chap. 10), the suprahyoid and the infrahyoid muscles of the throat and neck create a state of muscular suspension through their action as antagonists, which firms the pharyngeal walls and stabilizes the larynx in the phonatory tube at any chosen position during singing (Figs. 47-48).

Fig. 44. Light Soprano Singing F Sharp, 672 cps, Vowel [i] Left, piano; right, forte.

Fig. 45. Dramatic Soprano Singing Middle C, 246 cps, Vowel [a] Left, chest register, forte; right middle register, piano.

Fig. 46. Bass, Spoken Sound, Vowel [a]

Source: Guiseppe Bellussi and Allesio Visendaz, “II Problema Dei Registri Vocali Alia Luce della Technia Roentgenstratigrafica,” Archivo Italiano di Otologia Rinologia e Laringologia, March-April 1949.

The hyoid bone serves as a central ring to which these two groups of muscles are fastened, and each group pulls in the opposite direction. Thus firmed, the hyoid bone provides a fulcrum for the quick, violent actions of the tongue during articulation in singing. Since the hyoid and the thyroid cartilage are connected by membrane and muscle, the larynx closely follows the movement of the hyoid bone in its ascending and descending movements.

Proper positioning of the larynx in the phonatory tube is a primary factor in the establishment of a sound vocal technique, for the domination of either muscle group will affect the length, tension, mass, and elasticity of the vocal fold and determine the volume of the pharynx. Each laryngeal position will affect the timbre and character of the voice and determine its function.

The singer’s problem is to select the laryngeal position which is most natural for him. Each voice has its own dimension and compatible laryngeal position for singing (Records 1-4, Band 6). If the larynx is depressed too far through the action of the infrahyoid muscles and sustained in such a position by the balanced muscular system described above, the resulting large pharyngeal space causes a dark, highly damped sound that is difficult to sustain and it also causes each phoneme to lose its integrity because of the extreme alteration of the coupled system. (See “Point, Projection, and Focus,” p. 236.) If the larynx is held too high, the uttered sound becomes blatant and colorless.

Fig. 47A. Suprahyoid Muscles From Clinical Symposia by Frank H. Netter, M.D. Copyright Ciba.

Fig. 47B. Infrahyoid Muscles From Clinical Symposia by Frank H. Netter, M.D. Copyright Ciba.

Fig. 48. Suprahyoid and Infrahyoid Muscles, Action
From Clinical Symposia by Frank H. Netter, M.D. Copyright Ciba.

The sensation of finding the proper open throat and laryngeal position in the middle voice is that of the first stage of a yawn. A yawn at the point of maximum muscular contraction is far too extreme for a good singing position, however, the expanded throat sensation must always be accentuated as the pitch is raised. The singer and the teacher must remember that the suprahyoid and infrahyoid muscle groups always act as a unit in their antagonism and never as independent muscles. (See migration levels, Fig. 103, p. 234, all of the vowel sounds recorded within this work are sung with an open-throat position.)

The Suprahyoid Muscles

The suprahyoid muscles raise the hyoid bone and the larynx. They also firm the walls of the pharynx during singing. These muscles are responsible for tense and lax conditions of a phoneme. Place the fingers under the chin and pronounce [i], [I], and [ē] in sequence; notice the alternation of tense, lax, tense conditions. These muscles are genioglossus, stylohyoid, mylohyoid, geniohyoid, and digastric.

Genioglossus

Origin—Front of the mandible.

Insertion—Lower fibers to hyoid bone.

Action—Lifts hyoid and larynx, or when the hyoid is firmed by the infrahyoid, it draws the tongue down to the hyoid bone.

Stylohyoid

Origin—Cranium.

Insertion—Hyoid bone.

Action—Raises hyoid bone and larynx.

Mylohyoid

Origin—Mandible.

Insertion—Hyoid bone.

Action—Raises hyoid bone and larynx.

Digastric

Origin—Fore part of lower jaw. It forms a V shape as it passes through a tendonous loop to its point of insertion.

Insertion—Mastoid process.

Action—Raises the hyoid bone upward and back.

Geniohyoid

Origin—Mandible.

Insertion—Hyoid bone.

Action—Raises the hyoid bone and the larynx.

The Infrahyoid Muscles

The infrahyoid muscles lower the hyoid bone and depress the larynx. They also firm the pharyngeal walls during phonation. They are sternohyoid, sternothyroid, thyrohyoid, and omohyoid.

Sternohyoid

Origin—Sternum and clavicle.

Insertion—Hyoid bone.

Action—Depresses the hyoid and the larynx.

Sternothyroid

Origin—Sternum.

Insertion—Side of thyroid.

Action—Depresses the larynx, draws the thyroid cartilage downward, or assists the cricothyroid in tilting the thyroid cartilage forward and downward.

Thyrohyoid

Origin—Side of thyroid cartilage.

Insertion—Front of hyoid bone.

Action—Draws hyoid bone downward and depresses the larynx.

Omohyoid

Origin—Clavicle.

Insertion—Hyoid bone.

Action—Depresses the larynx and hyoid bone.

THEORIES OF REGISTRATION

Vocal Registers

The exact cause of registration in the singing voice is unknown. For those who seek specific information to perfect a teaching technique, the confusion of principle and terminology in voice teaching is indeed disappointing.

Professional singers more than teachers tend to believe that vocal registers do not exist. Most professionals are natural singers who have perfect body coordination and have never really confronted a register problem, or perhaps register breaks which did occur have disappeared with maturation. The average singer conceives of the vocal scale as one long extended register. His artistic goal is to pass from one register to another diatonically or intervallically without a noticeable change in quality, but the single register is more often an objective in teaching than a reality in the student voice. Many teachers believe that the head and the chest are the only registers. However, just as many believe that three registers exist (the head, middle, and chest). Despite the confusion in terminology, singers continue to sing an even scale and teachers continue to theorize.

In the human voice, registration is a physiological and an acoustical fact. Years of research by European teams¹⁸ have contributed evidence of its existence and have verified that all voices have three registers that may be utilized in singing, but this research has contributed little information on their function. They define the vocal register as follows:

A register within the human vocal scale is a series of sounds of equal quality. The musical ear distinguishes them from another series of sound also of equal quality. The limits of each series are marked by “points” of passage sometimes called “lifts.” The timbre of each series, or register, is the result of a constant rapport of harmony. To the male singer the primary register change at the upper part of the scale gives a certain vibrating sensation perceptible to the head. To the female the primary register change at the lower part of the scale gives a certain vibratory sensation to the chest. Each area of identical quality depends upon the adjustment of the resonating cavities.

Registers are produced by a mechanism that functions in the production of sound. The principal characteristic of this mechanism is the manner in which a particular laryngeal vibration is coupled with the supraglottic (area above the vocal folds) and the infraglottic (area below the vocal folds) resonators.¹⁹

Since one octave separates the masculine and feminine voices, the point of transition from the chest register to the head register for women occurs at the same height in the scale. Therefore, the point of transition occurs by acoustical law and through an adaptation of the total resonating space, always on the level of the same frequencies, E flat, 311 Hz and F 350 Hz.

All pitch skips that involve moving from one register to another demand a conscious adjustment of the coupled resonating system and the phonatory mechanism in one synchronous act. Enlargement of the resonators is no more important than controlling the vocal folds. Each act must complement the other.

At the moment of passing (transition between registers), the position of the larynx in the phonatory tube changes much more in the trained voice than it does in an untrained voice. The greater change results from the trained singer’s attempt to enlarge the pharyngeal resonators by yawning and simultaneously stabilizing and tilting the thyroid cartilage forward, thereby tensing the vocal folds (Fig. 27).

The single-register voice is not altogether a matter of vocal education. Some voices, through practice, may become homogeneous and uniform in quality and emission, but such an achievement is hardly within reach of all voices. A beautiful voice that fulfills the ideals of Western vocal culture is a gift of birth, and methodical teaching is not the principal element in its production.

Manuel Garcia’s Theory of Registration

The theory of registers advanced by Manuel Garcia, frequently quoted by teachers of singing, should be considered. Garcia achieved fame as a teacher and for his invention, the laryngoscope, which is widely used. He said:

Every voice is formed of three distinct portions, or registers, namely, chest (lowest), medium (middle), and head (highest). [These names are incorrect but accepted.]

A register is a series of consecutive homogeneous sounds produced by one mechanism differing from another series of sounds equally homogeneous, produced by another mechanism, whatever modifications of timbre or strength they may offer. Each of the three registers has its own extent and sonority which vary according to the sex of the individual and the nature of the organ.²⁰

The chest voice in women was considered by Garcia to be strong and energetic; however, he believed that it should not be used above the notes e flat and e natural, for to do so would abuse it. He also believed that the middle register is of equal extent in all female voices, that it differed only in strength and quality, but that it too frequently was veiled and weak.

Garcia believed that the head voice (Fig. 49) is the highest and most sonorous and that it possesses the power of penetration. He observed that in robust voices the medium register blends easily with the head register, but that in weak voices the union is unstable and often broken.

Registers in the Female Voice (After Garcia)

Garcia believed the middle and upper registers in male voices were remnants of the adolescent voice, and considered the entire singing range of the male voice to be predominantly chest voice. The tenor has greater skill in using the falsetto or head register, but he blends the top notes by using the closed or dark timbre (Fig. 49).

Registers in the Male Voice (After Garcia)

Closed and Open Tones

The terms closed tones and open tones are synonymous with closed vowels and open vowels (Figs. 74A and 74B, p. 229). They are used interchangeably with the terms covered tones and uncovered tones. These terms are rooted deeply in the traditions of voice teaching and generally have been accepted by phoneticians and voice scientists. Luchsinger²¹ has stated that the term cover or the use of the darkened vocal timbre as a device for bridging into the upper voice was first exploited about 1830 by French singers, notably Duprez. Up to that time the voix blanche or the white tone was preferred. Diday and Petrequin²² described the new technique as “voix sombres, couverte, ou en dedans” (dark voice covered within the larynx). The physiological descriptions are similar to our present understandings of low, stable laryngeal positioning and an enlarged resonating system.

However, most phoneticians describe such vowels as being tense (closed) or lax (open). These descriptive words indicate the degree of muscular tension present in the uttered sound. The bright, ringing quality present in the open vowels and the veiled, softer sounds of the closed vowels are not caused entirely by an alteration of the coupled system (Fig. 74). Gordon Peterson^* of the Bell Telephone Laboratories has explained the change in vocalic quality in these words:

The walls of the mouth and pharynx can be changed in texture by changing the tension of the musculature of the lips, tongue, and pharyngeal walls. As a result, the reflection of selected overtones is modified, so that the timbre of the vowel tone being uttered is itself modified, or even shifted in the direction of a different vowel. The difference between [i] and [I], for example, and between [u] and [U] are apparently achieved partly by a change of muscular tension in the tongue, though typically there is also change in the size of the mouth cavity. This change of lingual tension can easily be detected by placing the thumb and forefinger under the lower jaw and pressing firmly against the tissue below the tongue while pronouncing [i]-[I] and [u]-[U]. It may be concluded that when the inner surface of the mouth cavity, especially the floor, is firm, the cavity selects from the tone complex the proper combination of fundamental and overtones to produce [i], while the musculature is soft, the cavity selects the combination appropriate for [I]. In similar fashion, firm cavity surface helps to produce [u], soft surface to produce [U]. Accordingly, [i], [u], and the like are called tense vowels, and [I], [U], and the like, lax vowels.²³

These terms identify changes in tone that may be detected by the ear, and as such, they also identify the vocal adjustment that enables a singer to pass evenly from the middle register to the upper register. The “covering” mechanism of transition from the chest voice to the upper voice is used primarily in male voices. It is always effected with the closed vowel—the reason for “covering” is to avoid the open vowel sound. The contralto and the dramatic soprano may sometimes use it, but the soprano and coloratura soprano do not use it at all because the point of primary transition occurs on the low pitches of the female voice (Fig. 51). This adjustment in the male voice commonly is taught by imitation or by trial and error, since the exact nature of the action is unknown.

The terms open and closed have been used extensively by teachers of bel canto, the vocal techniques of the eighteenth century, which placed emphasis upon beauty of sound and brilliance of performance rather than on dramatic expression or romantic emotion.

One of the objectives of the singers of bel canto was the development of a vocal scale that was pure, unbroken, and uninterrupted. The transition of registers—either up or down the scale—demanded a modification in the tonal color of the topmost notes to prevent them from becoming disagreeable and harsh and to preserve the quality of the vowel sound as well as an even tonal line. The bel canto expression, “All vowels must be modified in the head voice for the sake of beauty,” has caused teachers to use the modifications of vowels as a means for transition into the upper voice.

The voice of a man or woman of college age is a voice in transition, and the vocal problems confronted by such a person are numerous and varied. Seldom is such a voice stable and mature. The problems of range and register are a concern of the teacher, but they are doubly important to the impatient student. Therefore, the attempt to develop range in itself is not wise, for to do so makes the problem a primary objective of both teacher and student; in many instances, such an objective has become a studio fetish.

The basic phonatory position of the closed vowel or covered tone and its transition into the upper voice may be taught to any male student after he has acquired a knowledge of phonetics and after he is able to reproduce vowels in both open and closed position in both speech and song.

The most important factor in the selection of the proper phoneme (vowel position) by a singer is his awareness of the manner in which the resonators are coupled to produce a particular vowel sound (Fig. 75).

Transition for the Male Voice

Teachers of singing realize and research verifies that all voices have three registers that may be utilized in singing. Each register is separated by a point of transition; these points are indicated upon the diagram in Fig. 51. The pitches upon which these points are found depend upon the character of each individual voice and its tessitura. Thus, the point of passage may vary a major second above or below the pitch suggested.

In male voices the transition most likely to be evident to the performer and the listener is the transition from the middle register to the top register because the change is effected by alteration of the phonatory mechanism as well as a change in the resonating system. However, in many voices this transition point is not evident to the listener, nor does it pose a problem to the singer. The lower points of transition are as follows:

Fig. 49. Registration Chart (After Tarneau)

They are evident only in the beginning singer’s scale and do not need special pedagogical technique.

In making the transition into the upper voice, an instantaneous coordination of respiration (breath support), phonation (unrestricted vocal sound), and resonation (forming the proper vowel) must occur; otherwise, the transition will seem awkward to the listener, and uncomfortable and unstable to the performer. The upper points of transition are as follows:

The student eventually will discover the ideal coordination of these four forces by directives from his teacher. Here he needs to examine visually only the position of the resonators and articulators during such a transition. (See the kinesiologic analysis, Chap. 10; the student may examine the same transitions aurally on Records 1-4, Band 5.)

All transitions into the upper voice by the male singer are made with a closed vowel. The back vowels [u] and [o] and the central [ʌ] are vowels that make this transition automatic. All covered vowels are closed sounds. The [ʌ] as in up is considered neutral and more “singly resonant” than other phonemes and, although it is an open vowel within the staff, from top space E it becomes a closed neutral sound. Teaching this transition by using an open vowel sound is not possible because, when the male sings notes above top space E, treble clef, the sound becomes disagreeable and harsh.

The student has more difficulty learning the transition into the upper voice by using the central vowel [ɑ] or any of the frontal vowels. The easiest procedure is to start with [u] as in food and progress clockwise around the vowel triangle until the frontals are reached and mastered. (Consult Chap. 9, for complete register changes and the recordings for performance of such changes.)

Transition for the Female

In the female voice the transition from the middle to the lower chest register—

is most evident to both singer and listener because the transition is effected by an adjustment of the phonatory mechanism. A woman may have a strong muscular adjustment of the larynx and throat, which permits her to make this transition downward and upward into the chest voice with no evidence of a change in quality. However, such singers are the exception and not the rule. The chest voice is a necessary part of the female singer’s vocal range and should be so conceived and developed.

The female problem of bridging occurs while making the transition downward from the middle voice into the chest voice (black area, Fig. 49) or upward from the chest voice to the middle voice.

Most experienced female singers tend to extend the chest quality to—

in formal singing. They should never carry the chest quality or mechanism above—

The higher this quality is carried, the more difficult and obvious the transition becomes, and the more strident the voice sounds.

In making the transition from middle register to chest register descending, a female singer usually “feels” a change in mechanism, she decreases vocal force by using less energy and by slightly lowering the jaw. She attempts to “ease” her voice into the lower registration mechanism. The basic vowel is always maintained through this pitch change—ascending or descending without modification.

The quality of the middle voice, that pitch area from—

should become the model quality for notes below—

The female singer should avoid excessive vocal force while singing chest area.

The secondary point of transition for the female voice occurring suggested pitch—

is not evident to the listener, but it is evident by its instability to many singers as they attempt to pass into the top register by pitch skip or by diatonic scale. Descending scales sung on the neutral vowel [ʌ] help to strengthen this point of transition.

The Adduction of the Vocal Folds

Pressman attributes the primary change in register, or the “break” in the voice, to the moment of adduction of the posterior portion of the thyroarytenoid evident in the production of pitches which lie above the point of transition in the male voice. (See p. 92.) Such a premise assumes that an identical change in mechanism will occur in the female voice at the primary register change into the chest voice. (See p. 93.) It assumes that the female can sing all of the tones above chest voice with a portion of the vocal folds in adduction, that is, with the posterior portion of the folds in adduction, as in Fig. 34 never as in Fig. 33. This theory is most plausible and could be the answer to changes in sensation experienced by the male or female singer at such points of transition. However, adduction may or may not take place in all voices. Variation of laryngeal function as well as breath pressure may be employed. (The detailed synthesis of damping and register change is described on pp. 89, 92, and 119.)

Physiological Changes. Studies at Indiana University, using tomography and cineradiology (X-ray motion pictures)²⁴ as a means of analysis, reveal that, during the transition from a low pitch on which an open vowel is sung to a higher pitch above the register change on which a closed vowel is sung, the larynx is lowered an average of three to five millimeters in forming the front vowels and five to eight millimeters in forming the central and back vowels. This act of lowering the vibrator (vocal fold) causes the entire phonatory tube, extending from the oral cavity to the bifurcation of the trachea, to increase its basic dimension, this increases the coupled system so that the pharynx becomes the primary resonator.

The physiological changes which occur at the point of passage at the primary register change in both male and female are illustrated in Figs. 50A and 50B. (The sound resulting from these changes may be heard on Records 1-4, Band 5.) The laryngeal alterations sound bilabial.

The anatomical alterations shown in Fig. 50A and 50B are most dramatically displayed as the singer sings the open and closed positions upon the same pitch, E natural for the bass voice and C-256 for the mezzo soprano. The singer must remember that, when he is moving through the point of passage, ascending or descending, muscular control of the laryngeal position and alterations of the dimension of the resonating system will cause this change to occur gradually.

This enlargement of the resonating system is necessary to accommodate the alterations in the laryngeal function which occur at the point of passage of the vowel sound. Perhaps the most significant physical alteration to be sensed by the male singer as he “passes” or “bridges” into the upper voice or by the female singer as she passes downward into the lower voice is the lowering of the larynx and the narrowing of the vestibule which determines the phonemic characteristics of the uttered sound.

As the larynx is lowered, it imparts to the laryngeal organs a stability they could not attain with the vibrator at a higher point and with the phonatory tube altered in width and length. The physical sensation experienced by the singer during the adjustment is primarily that of a yawn. The physiological action consists of lowering and fixing the larynx through the action of the antagonist musculature, described on page 84. The increased laryngeal tension also secures the adducted portion of the vocal folds and permits the margins of the reduced glottal aperture to become stable and to vibrate freely (Fig. 31B). These muscles act to depress the floor of the mouth, the base of the tongue and the larynx. The broadening of the supraglottic space results from the action of this muscular set, which, when combined with the firming action of the suprahyoid muscles, adds stability to the pharyngeal area through an opposing action.

Fig. 50A. Radiographs of Male Voice at the Primary Register Change

Superimposition of negatives display anatomical movement. Solid line——open vowel Dotted . . . . . line closed or covered vowel

Fig. 50B. Radiographs of Female Voice at the Primary Register Change

Superimposition of negatives display anatomical movement. Solid line——middle voice Dotted line. . . .chest voice

PEDAGOGICAL PRINCIPLES

Intensity, Laryngeal Function, and Registration

Constant singing within a proper pitch range and within controlled intensity limits will result in vocal growth, but the use of excessive range and excessive intensities may permanently impair the human voice. A proper pitch range is one which is suitable for a specific voice and not a class of voices; i.e., all sopranos do not possess the same tessitura, and what would be easy for one may be difficult for another. The same rule would apply to voices regarding the use of proper intensities. Too many singers sing pitches that are above their natural tessitura and sing them much too loudly, too constantly. Many authors have described the physical process by which the proper balance between pressure and resistance may be attained,²⁵ i.e., the balance between the driving force of the abdominal musculature, the resistance of the thoracic musculature, and the laryngeal controls necessary to produce a vocalized sound that will not result in a deterioration of the voice. Such pedagogy may only be taught by psychological systems, and to the singer, the residual concept of such a proper balance is always a sensation. He remembers how he felt when such a physical state was attained. (See “Support,” p. 11.)

The coordinate relationship of mental concepts of tone to respiratory and phonatory disciplines of the body in song has long been a most disturbing problem for the voice teacher. Contemporary scientific research of Pressman, Sonnonin, Rose, Van Den Berg,²⁶ and others has contributed a logical interpretation of this phenomenon which tends to support the vibrating-string theory.

A change in intensity always should be effected gradually by a disciplined coordination of the laryngeal muscles and the muscles of expiration. Such a change involves a gradual alteration of the length, mass, and tension of the vocal folds and a constantly increasing or decreasing breath pressure. Singers often effect this change by conceptual means, i.e., by attempting to avoid a change in quality (timbre) or by attempting to maintain a particular vowel color. Regardless of the pedagogy involved, the residual rule is that the change must be made gradually and smoothly.

The gradual change of intensity on a single pitch at the point of register transition, rather than diatonic drills which involve high tessitura, is the basis of the bel canto technique as reported by Mancini, Bernacchi, and Issac Nathan by Reid.²⁷ Such statements as those which follow give evidence of the importance of the coordinate control of the laryngeal action and the breath pressure in developing a firm singing technique:

The excessive use of the messa di voce, or swelled tone by early Italians was a persistent attempt to join the two registers.²⁸

As the early Italians always considered the art of singing to mean an absolute control over dynamics and an ability to swell and to diminish the intensity of the tone, the inference is plain that the registers are to be joined by swelling from piano to forte.²⁹

In the advanced stages of training, the performance of the messa di voce must be practiced continuously until there is an exact matching of both quality and intensity at each point of transition. After this technique has been mastered the break disappears. . . . This is the singing style known as Bel Canto.³⁰

Singing the Messa di Voce

An increase in breath pressure will elevate the pitch of a sung sound. Therefore, to sing messa di voce the pitch must be maintained while the breath pressure is varied. Such an act directly changes the amplitude of the vibrations of the vocal folds through the alterations of their length, tension, mass, and elasticity. This change in amplitude must be in direct ratio to the alterations of the abdominal and the thoracic pressure and must be accompanied by a fixation of the volume of the resonating space for each vowel that is sung.

In effecting the transition from a forte to a piano sound, the amplitude of vocal fold vibration will decrease. The decreasing abdominal pressure will result in less breath flow. The thoracic, or diaphragmatic, pressure will increase and cause a sensation of holding back the breath. The resonating space must remain open and expanded to the jaw position assumed during the production of the forte sound to preserve the integrity of the phoneme.

In effecting the transition from a piano to a forte sound the reverse is true. The amplitude of the vocal fold vibration and the abdominal pressure will increase. The thoracic pressure will decrease. To preserve the integrity of the phoneme and to accommodate the increased intensity, the volume of the total phonatory tract will increase.

Laryngeal Action and Pitch Change^*

To sing a scale evenly, the same ratios of breath pressure to laryngeal control are employed as those employed in singing the messa di voce, for the ratio between pitch change and the increase of intensity in a sung scale passage should be constant.

The thoracic and diaphragmatic pressure should be increased gradually as the pitch is raised to give the singer the sensation of holding back the breath. If this control is not achieved, the scale becomes much louder as the pitch rises. Drills must be devised to teach the voice student how to develop these controls lest he learn a process of singing in which he cannot vary intensity throughout the scale and in which he depends upon the same intensity for the production of all song.

VOCAL PEDAGOGY AND LARYNGEAL CONTROLS

The following statements by Pressman are a summation of the application of the foregoing theories of respiratory and laryngeal functions as they may be applied to a teaching process.

Because of variations among persons in the length, breadth, general outline, and tension of the vocal folds, as well as in habits concerning the degree of the expiratory force utilized in producing tones, production of any given tone in different subjects by exactly the same mode or method of laryngeal action is impossible. Even two persons with strikingly similar voices of exactly the same range are not likely to produce a particular tone in exactly the same way. Each singer will vary in concept of tone quality, vowel postures, and breath support. If, for example, one singer uses slightly less expiratory force than the other in producing an exactly equivalent tone, the diminished air pressure must be compensated for by an increased approximation or by tension of the vocal folds. For instance, one singer may even need to bring the posterior tips of the folds into contact for adduction, whereas this would not be necessary for the singer who utilizes a greater force of expired air. Thus, two singers can produce the same sound in two different ways. Yet, these differences in expired air pressure and laryngeal configuration may result not only in the production of the same tone, but the volume of the sound thus produced may also be exactly the same. Differences in the resonating system of the two persons and other indeterminate characteristics account for production of the same tone even though the expiratory pressures and the contour of the vocal folds remain the same.

Therefore, one can never ascribe a particular laryngeal picture to the production of any given tone. However, certain broad general principles do apply, and with respect to any larynx, one can predict within certain limits what changes will take place in that larynx as one begins at the lowest note which the particular larynx can produce and ascends the scale to reach its highest possible note.

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^*The use of vocal folds instead of vocal cords in this work preserves the concept of the fold as a functional wedge of flesh whose inner fibers are altered in length, mass, tension, and elasticity mentally by the singer. Vocal cords is suggestive of the segmental vibration of a string in which mass, tension, and elasticity are unalterable.

^* For specific action of this musculature, see Chap. 2, “Respiration.”

^* This movement is evident in X-ray photographs which appear in Chap. 10.

^* In Claude Merton Wise, Applied Phonetics, 1957. Reprinted by permission of Prentice-Hall, Inc., Englewood Cliffs, New Jersey.

^* See also p. 69.