I remember learning in General Science in elementary school that “water seeks its own level.” I can still visualize the experimental equipment: a large glass chamber, consisting of many turrets of different heights and varying widths—some rectangular, some cylindrical—all open at the top and all sharing the same large base. When water was poured into one of the “stacks” it fell directly into the base and gradually rose evenly and to the same level in all the stacks. It didn’t seem to matter how wide or narrow they were. The water rose to the same level in each of them as long as it was being poured. I was convinced. Water certainly did seek its own level.
Years later, in a college physics laboratory, I saw the same kind of experiment performed again. But this time the equipment was slightly different. Some of the stacks were tall and very thin, with tiny diameters. The water rose higher in those tubes than it did in the vessels of greater diameter. The narrower the tube, the higher the level! This phenomenon was explained as “capillary attraction.” The water tended to adhere to the walls of the various stacks. Indeed, it adhered to all the walls. You could see that the liquid “sloped upward” toward all the walls, even in the larger vessels. Some of the vessels were so narrow that they didn’t have enough of a central area where the water could “sit” at its basic level, so the level itself appeared to be higher.
Did the second experiment disprove the first? Of course not! Water does seek its own level. Capillary attraction is a refinement of the original truth, a greater insight into the truth.
We may encounter many examples of this sort of thing in our learning experiences. At first, we learn basic fundamentals. Later we discover refinements, some of which may seem to contradict the fundamentals. If we continue to experiment, and apply logic and wisdom, we may add to our fund of knowledge and to a deeper understanding of the fundamentals.
As a teacher of advanced viola students, I find that much of my time is spent in explaining and demonstrating refinements of what they were previously taught. I occasionally find that I have to teach the opposite of what was originally taught by their first teachers. But most of the time, when I tell a student to do something differently, I am teaching a refinement. I am explaining the capillary attraction that leads to a better understanding of the original water-level concept.
One of the first things learned by all beginners on the violin or viola is to “keep that elbow under” the instrument. This is absolutely necessary, of course, but it seems so unnatural at first, and completely different from anything the student has ever done with his left arm. There is nothing more difficult and uncomfortable, at first, than twisting the arm into that awkward contortion that gets the left elbow directly below the fiddle—and nothing more annoying and irritating than the constant nagging to “keep it there.” I have the greatest sympathy for all such beginners. What they are asked to do with the left arm is not merely unnatural; it is actually painful! I’m sure that thousands of beginners give up after a few weeks of this torture and that is why there are so many pianists and guitar players—and cellists.
What is surprising to me is that there are so many violinists and violists (the “chin-strings” as George Szell used to call them). And what is amazing to me is that so many of them are playing their instruments “the hard way,” with the left arm contorted much more than is necessary. Not only students but many professionals as well go through life with their left arms twisted far beyond what is required by their fingers. I have seen fiddlers (and that includes violists) who have their left arms so far “under” that they would be able to play their instruments with the scrolls pointing straight ahead of them if that were desirable. Instead, they play with a tremendous bend of the left wrist in order to be able to place their fingers on the strings where the instrument is actually positioned. They play virtually everything with the same rigid left-arm position. The arm is under far enough to enable them to play on the C-string with a rich, mellow tone. As they go across the strings, the sound gets drier and thinner, and when they play on the lower A-string, the sound is nasal and metallic and the vibrato is practically nonexistent. As they go from the lowest string to the highest, with the left arm unyielding, the fingers become more arched, until they are playing on the very tips, with the fingers almost tightly clenched on the highest string.
Of course, the pain is no longer present, or maybe it still hurts but they have become used to it. In any case, the tension must be tremendous, and tension is the enemy of the string player. It affects the sound, the shifting technique, the ability to adjust pitch, and the stamina and general efficiency of the left hand. There is nothing worse for the technique than the exaggeration of something that is not natural in the first place.
One of the joys of teaching is seeing the light come into a student’s eyes and hearing that sigh of relief when I simply relax his wrist and elbow over to the left without changing the position of the viola. He then realizes that his arm, hand, and fingers are comfortable and that the natural finger contact on the string is with the fleshy part rather than with the extreme tip—a definite advantage for sound on the viola. This position is so natural and easy. Why should it come as a sudden revelation to so many? Because of the Golden(?) Rule: “Keep that elbow under.” If these players could relax the left arm, let it drift to the left as they go across to the higher strings, they could play on each string with the same arching, the same point of contact, the same feeling on each string—and, most important, the same rich, mellow sound.
The left arm should be under the instrument as much as is required by the fingers, and no more. This means, of course, that it must be well underneath when playing on the C-string, especially in the upper positions, and even more so when reaching for an extension with the fourth finger. The left arm should relax as the fingers go to the higher strings, and then, of course, it must come under again as the fingers continue into the higher positions, where the hand needs to get around the body of the instrument. Here, it is not enough that the arm merely come under more, it must also come up so that the hand may rise over the body of the instrument—but that is another matter.
The important point to remember is that while water does seek its own level and the elbow does need to be under the fiddle (generally), the left arm must be flexible. It must be as relaxed as possible at all times and come under more only to meet the requirements of the fingers.
Another thing that is almost universally taught is to “leave the fingers down.” I can see why this is necessary in the early stages. The beginner has no feeling for a set hand and arm position and if he lifted one finger when placing another, the hand and arm would probably center on the new finger. It would probably be impossible for the teacher to mold the pupil’s hand into a proper first-position alignment. Another reason for the “leave the fingers down” admonition is that the pupil’s ear is not yet developed. He is likely to be careless about exact pitch. The teacher feels that if he can get the pupil to leave the fingers down on the correct pitches on the way up the scale, then they will be in tune on the way down. This is fine and probably quite necessary—for beginners. As a matter of fact, any fine string player will do this when he is playing fairly rapidly and will have to play the same notes descending that he just played ascending, but this procedure is not necessary and is often detrimental when playing slowly and expressively with vibrato.
The best and most natural sound is produced with one finger at a time. The wrist vibrato, especially in the case of the fourth finger, is limited in scope when all the fingers are down. The most harmful manifestation of leaving unnecessary fingers down is tension, particularly in the case of those students who tend to press the fingers down hard—and I’m afraid that means most of them. Time after time, a new student will play a slow scale for me, leaving each finger glued to the string (and pressing that string into the fingerboard) until the fingers are needed for a note on the next higher string. Fortunately, this cannot be done on the way down because each finger has to be lifted in order for the next one to sound. One of my first teachers told me that leaving fingers down was an aid to facility and speed because the fingers were already there when you needed them to go down the scale. To this day, I cannot appreciate the advantage of being able to play down the scale faster than you can play on the way up!
One of my pet peeves that derives from the “leave the fingers down” syndrome is the sloppy passage work and unwanted grace notes I hear so often from new students. In playing a rapid group of four sixteenths such as: c d e c (2 3 4 2), they provide me with a bonus—a fifth note in the group of four, a little grace note d between the e and c, a little mess between the third and fourth notes in the group. Since such composers as Haydn, Mozart, and Beethoven wrote thousands of such note-groupings, I get to hear this bonus quite often, in fact, ad nauseam. What amazes me is that I’m the only one who seems to notice. The student never seems to know what I’m talking about when first I bring this to his attention.
If you play 2 3 4 2 rapidly, leaving the third finger down while you play the fourth, and then try to lift 3 and 4 simultaneously, the sound probably isn’t going to be clean. The fourth finger is shorter than the third and comes off more easily (it has a greater distance to go when lifted because of the alignment of the hand), thus the third-finger grace note.
I try to have my students lift the third finger while the fourth is down so as to avoid the mess between 4 and 2. The third finger does not have to be lifted high; in fact it can’t be, it just has to be released. More often than I would care to say, the students are simply unable to lift the third finger while the fourth is down, so deeply ingrained is the habit of leaving the fingers down. They can lift the third if they also lift the second, but that should not be necessary, nor is it desirable. However, I would advise lifting both 2 and 3 when 4 is down if that is the only alternative to producing the unwanted grace note.
The same thing often happens with 1 2 3 1 groups and even with 0 1 2 0 groups. Here the cure is easier because no one has much trouble learning to lift 2 while 1 and 3 are down, and lifting 1 when only 2 is down is no problem at all. Nevertheless, I often have to point out the grace-note mess when these fingerings are used. Students have to practice lifting the fingers that tend to produce unwanted notes before those fingers can do damage.
Another undesirable manifestation of “leave the fingers down” occurs when playing chords. It seems the most natural thing to me to lift the finger or fingers on the lower two strings when the bow has already rolled over to the upper two. But student after student plays on the upper strings with the fingers still glued to the lower ones— with the arm too far under for the upper strings, the fingers on the upper strings tense and cramped, finger contact on the very tips, tight and narrow vibrato (if any at all)—and complains about how hard it is to play chords in tune!
When breaking four-string chords into two and two (which is the way they are almost always performed), it is not necessary to place the upper-string fingers until the bow is rolling over to those strings. Then those fingers can be placed with the left arm relaxed over to the left so that the point of contact is with the fleshy part of the fingers (the arm, hand, and fingers relaxed), and with the lower strings released so that a good, rich vibrato can be produced for the duration of the chord. Naturally, this applies to three-string chords as well. The basic rule is: Release the finger that you no longer need to depress, especially if it causes discomfort or technical difficulty.
Also, when playing arpeggiated chords, as in Harold in Italy by Berlioz, it is sometimes advantageous to lift fingers from the lower strings while the bow is on the upper strings and vice versa. This aids intonation, enables the hand and fingers (and arm) to remain relaxed, and often permits easy replacement on new notes when the chord changes in the middle of a group of sixteenths.
There is a passage in the first movement of the Bartók Viola Concerto (on the fifth page of the solo part) that consists of arpeggiated chords across the four strings, articulated as two notes slurred and two separate. These chords lie in the fourth, fifth, and sixth positions and are full of perfect fifths. Student after student has told me that this passage is impossible, and, indeed, it would seem so at first glance. I remember my first encounter with these chords. When I tried to play the fifths, the finger would go down between the two strings. Of course, the harder I pressed, the more the finger went between the strings, separating them even more.
The solution to the problem of the fifths lies in using minimal finger weight and lots of flesh contact with the strings and, most important, a flexibly rolling left arm. Actually, the flexible left-arm concept enables you to deal with one string at a time, literally rolling the finger from one string to another. The left arm, in general, should be “under more” for the lower strings and should relax to the left for the upper strings. When one has a freely rolling left arm and lifts the fingers not required at the moment (especially the fingers that are about to be used on other strings), the entire passage becomes eminently playable—clean and with correct intonation. Of course, it is the lifting of the fingers that enables the arm to roll freely. The technique does take practice and coordination. It is not easy, but neither is it “impossible.”
I have already alluded to “pressing the strings into the fingerboard.” I suppose that this is another of those necessary evils. The beginner has weak, undeveloped fingers that are likely to wander from the pitch if insufficient pressure is maintained on a given note, but I wish that students would not exaggerate the benefit of pressure to the extent that it becomes a problem for the rest of their lives.
I was specifically told by one of my early teachers that the softer I played, the harder I should press my fingers down. I understand why this was told to me. The excitement and intensity of playing loudly would insure sufficient pressure to keep the finger in place, whereas playing softly might cause me to let up on the weight too much. But the advice to press hard is very bad advice, indeed.
Pressing too hard builds calluses on the fingertips, digs grooves in the fingerboard, and wears the strings and causes them to become false. Much worse: it causes tension in the fingers and hand, which affects the vibrato and the shifting technique. I advise my students to experiment in order to determine how little finger weight they need to produce a clear sound. I have them play something fast, an etude or a perpetual motion, with no finger weight at all, to begin with. This produces whistles and harmonics, for they are just playing on the surface of the strings. Then I tell them to increase the weight of the fingers gradually. To their surprise, they find that almost immediately, before the strings have begun to touch the fingerboard, they have already achieved clarity in sound and pitch. I then advise them to go beyond that and depress the strings all the way, so that the strings make contact with the fingerboard. This insures that there will be enough downward pressure. Sometimes, when the vibrato is very fast and intense, I advise using a little extra weight to insure that the finger will remain anchored. But I certainly do not believe in pressing hard at any time, and I advise using less weight when playing fast passages where no vibrato is involved.
This is one area in which I’m a real nag as a teacher. It isn’t easy to keep from pressing too hard with the fingers, and students need constant reminders to relax the finger weight, especially when shifting. After all these years of knowing better, I still catch myself digging the string into the fingerboard in moments of great musical intensity. It is a continuing battle to remain physically relaxed when in the throes of intense emotional climax, but that is what produces the most effective result on the viola.
I teach tone production through relaxed weight of the bow arm. The arm rests on the bow through the index finger of the right hand; and the weight of the arm is directed onto the string by the arched right thumb, on the underside of the stick to the right of the index finger. This sounds complicated on paper, but it is very natural, and it is the way most fine violists play, whether or not they think about it in those terms. I believe that it is very healthy to think about it in exactly that way. The more sound desired, the more weight is relaxed onto the string—through the first finger. If the bow arm is more relaxed, it is likely that the left hand will be relaxed and that the fingers will not dig the string into the fingerboard.
On the viola it is very important to play with the flat hair in the upper half of the bow, with the wood directly above the hair. (I was taught by my first teacher to play with the stick turned away, to play on the “outside” of the hair. But I can’t fault my teacher in this case, for I started on the violin.) Most people think that the big difference between the violin and the viola is felt in the left hand, for the notes seem to be so far apart on the viola. True, the reaches are greater for the left hand, and a violinist with small hands will have quite a problem trying to adjust to a viola. But a bigger problem would be having short arms, for the real difference in feel between the violin and the viola lies in the bow arm, in the distance between the body and the point where the bow and the string meet. When I try to play a violin, I feel as though I’m bowing right under my nose. The violinist trying a good-sized viola for the first time will find that he has to reach way out to place the bow between the bridge and the fingerboard. To make matters worse, the viola generally responds better when played farther away fronj the bridge than is the case with the violin. Therefore, while it is possible (perhaps preferable for people with longer arms) to play the violin with the bowstick turned away and still produce a big, relaxed sound, that is not advisable when playing the viola.
If one is to produce the sound by relaxing the weight of the bow arm downward, it is necessary to have the right wrist low in the upper part of the bow, especially at the tip. With the wrist down, the entire right arm feels its weight being relaxed downward; and with a relaxed right arm, a relaxed left arm is achieved naturally. Playing with the flat hair in the upper part of the bow is the way to attain this relaxed feeling.
Of course, when approaching the frog on an up-bow stroke, the stick may be (in fact, must be) turned away. But at the frog great weight is not needed, and it is possible to maintain a relaxed wrist and arm there even though the wrist may be quite high. Then, on the down-bow stroke, the stick should gradually be returned to the position in which it is exactly above the flat hair, at the same time the wrist gradually drops down in order to turn the stick. By the time the middle of the bow has been reached, the hair is again flat and the weight of the arm is again relaxed downward.
The turning of the bow toward the flat hair position and the lowering of the wrist on the down-bow stroke are not merely simultaneous. One is actually the cause of the other. The same thing is true on the up-bow stroke. On approaching the frog, the bow stick naturally turns away and the wrist naturally rises. I say that this happens “naturally” because it really does. Any attempt to fight this tendency by insisting that the hair remain flat all the way to the frog would result in a very uncomfortable sideways turn of the wrist.
One area in which I’m very likely to suggest “refinements” is in shifting. When many of my new students first play for me, they have no shifting technique at all. In fact, many of them have no legato either. They jump quickly from one position to another, making no connection between the notes involved and often releasing the weight on the bow as they jump from one note to another, thus insuring a complete disconnection. The modern student is so afraid that the shift might be heard, that he doesn’t shift at all. The fear is founded, I believe, on the way that shifting is usually taught.
Perhaps it is necessary to teach an entirely “positional” method of shifting at first, in order to get the concept of positions across to the student. I was certainly taught that way. I remember being told that to go from an e (first finger, first position on the D-string) to a b (third finger, third position on that same D-string), it was necessary to slide my first finger up to a g, so that my hand would be in the third position, and then I could plop my third finger down on the b. In other words, in order to play an e going to a b on the same string, I had to play a little g in between.
That wasn’t so bad. Of course, there was no g grace note between the e and the b in the music, but g is between e and b, and there might be an e minor chord involved, so what harm could the little g do? (Kreisler used to make shifts like that sound gorgeous.) But now consider this: A shift down from g (first finger, third position on the D-string) to an f♯ (second finger, first position on that very same D-string), a shift of a half-step! I was taught to slide my first finger (hand, arm, and all) down to an e in the first position (that’s where I was going, wasn’t I?) and then to add the second finger on the f♯! Now that is another matter. There is no e between g and f♯. In fact, there is no room for anything between g and f♯. Can you imagine what that kind of half-step shift sounded like? Is there any wonder that students spent the rest of their lives trying to obliterate the sound of such shifts?
I do not teach “positional” shifting. I have nothing against positional alignment of the hand. In fact, I insist on it. A positional concept is absolutely necessary for knowledge and mastery of the fingerboard, for fingering concepts, for control of intonation, and for stability and solidity of the left hand, in general. But one should not shift from one position to another position. Shifting should be done from one note to another. Positions are for being somewhere, not for going there. It is really so utterly simple: you have notes to play and fingers to play them with. You do this by ear with a relaxed hand and everything falls into place, naturally and easily.
Let’s go back to the little half-step shift from g with the first finger back to f♯ with the second finger. Positionally (third position to first position), it is a shift of a minor third. But if you think just of the notes you have to play and the fingers involved, you only have to drag the first finger back (releasing the weight) a half-step to f♯ and replace it with the second finger. Of course, the first finger must move back (with no weight at all) a little farther in order to make room for the second finger on fit, but not nearly as far back as e! Then, with the second finger already sitting on the f♯, relax the hand and arm back into the first position so that you can play an e with the first finger if you need to. But no extraneous pitch will have been heard between the g and the f♯, and there is no need to hide the sound of the shift or risk destroying the legato connection between the two notes.
I teach shifting in three steps: relaxing the hand in the direction of the shift before leaving the old note, relaxing the finger weight during the actual transfer of the new finger to the new note, and relaxing the hand and arm into the new position as soon as the new finger is in place so that one is ready to play the next note in the new position. After a while, steps two and three merge (the relaxing of the hand and arm taking place immediately, as soon as the new finger goes down on the new note). This leaves only the relaxing in the direction of the shift to be done in advance. There is some relaxed reaching toward the new note, which cuts down the actual distance traveled (without weight) by the old finger.
For example, in the shift from e to b (first finger to third on the D-string), the hand would be relaxed upward while the e was being played with the first finger. The third finger would be “aiming” (reaching in a relaxed manner) upward toward the b. The weight would then be released from the first finger as the hand and arm (led by the “aiming” third finger) pulled the first finger up to about an f♯ (the exact location does not matter). The weight and the concentration have already been shifted from the first finger to the third, which now goes down (with full weight) on the b. Then the hand and arm relax fully into the third position before another note is played.
The differences are that the hand does not go into the third position until after the b is reached with the third finger; the first finger does not travel as far before the third finger is placed; and the fleshy pad of the third finger goes down on the b because the finger was extended on the way up. The important advantage is that it is the left hand that releases and controls the weight during the shift, not the right hand. Most of my students have been taught (not by me!) to release the weight of the bow during the shift. This does the job all right. It hides the shift, but it also destroys the legato.
It isn’t always such a great thing to hide the shift completely. Sometimes, in Romantic and modern music, a shift may be deliberately exposed to enhance the legato. When you have to change bow (because you’re running out) and you don’t want to change (because you want the line to go on) there is nothing like a rich, juicy shift to bridge the change of bow and continue the legato line.
Another thing that many of my students have been taught is to shift quickly. This goes along very well with the jump school, where there is no shift at all—just a quick skip to the new position. It is true, of course, that if you’re going to disconnect, it is better to get it over with quickly and get on with the legato as soon as possible. But, unfortunately, the faster the shift the more likely it is to miss. Also, I find that a fast shift in a slow tempo is jarring and out of place. It can seriously upset a quiet, relaxed mood.
It is difficult for a student who has been taught to shift quickly to unlearn this habit. I ask my students to practice scales slowly in order to develop the habit of taking time for leisurely shifts from the note just before the shift. They return a week later with very slow scales but with shifts occurring at the last possible moment and as fast as ever. It takes a while for them to develop the ability to control the timing of the shift and to do it correctly with evenness, smoothness, grace, and accuracy. Once developed, however, this ability is a real asset. The student feels that he always has plenty of time for the shift, even when playing very rapid scales, and he does not feel pressured or hurried.
The shift should blend into the tempo and mood of the phrase. It should not be a technical maneuver but a part of the musical expression. In this way, it becomes unobtrusive in the real sense. It is there but it does not detract from the music or get in the way. It adds to the mood and shape of the music.
Another thing that I was taught and that I have “refined” is the vibrato. When I was a student (in the 1930s) there was a fairly universal prejudice against the use of arm vibrato, especially on the violin. I had developed a natural arm vibrato that produced a very lush tone. This, undoubtedly, was one of the factors that contributed to my ultimate preference for the viola, for my vibrato produced a sound that was very attractive on the viola, but it often sounded sluggish, too wide, and “too fat” on the violin.
Long before I had ever heard of the viola, my early violin teachers tried to “get rid of” my arm vibrato and insisted that I learn to vibrate from the wrist. It was a difficult period, but I worked very hard and finally developed a useful wrist vibrato. I have never been sorry about that, but I am very happy that I never got rid of my natural arm vibrato.
The prejudice against the arm vibrato has largely fallen by the wayside. Hundreds of fine young violinists today (not to mention violists) have good-sounding and efficient-looking arm vibratos and use no wrist at all. Strangely enough, I think that they are missing a good bet. The wrist vibrato and the arm vibrato each have their special advantages, so obviously the violist who has the two types is more fortunate, both expressively and physically, than his colleagues who have only one. The muscles used to generate the wrist vibrato are different from those that produce the arm vibrato. Therefore, while one set of muscles is at work, the other is at rest. The violist who has a choice can go on playing all day (and professional musicians often do) without becoming physically tired.
It might be well to clarify a matter of nomenclature at this point. The two types of vibrato are popularly known as the “wrist” vibrato and the “arm” vibrato. It would make just as much sense to call them the “hand” and the “shoulder” vibrato. It is the hand that vibrates from the wrist as a joint. The arm vibrates from the shoulder as a joint.
The obvious advantage of the wrist vibrato is that the hand is a much smaller piece of equipment than the arm. When great speed is desired in the vibrato (for great intensity), the hand is much more efficient than the arm, and much more comfortable. However, most people with exclusive wrist vibratos avoid using the fourth finger on expressive notes because the vibrato is too narrow and the fourth-finger sound is thin. Unfortunately, I know too many “three-fingered” violists with pure wrist vibratos.
With an arm vibrato, one can produce all the width one needs with any finger, including the fourth. One can also produce a rich sound when playing octaves or thirds or, in general, when two or more fingers are down at the same time. With the arm, one can continue to vibrate with a rich sound while making extensions, up or back.
By varying the speed and width of the vibrato, one can produce a myriad of colors and moods. It really does not matter whether the vibrato is being produced by the hand or by the arm; nor does it matter which finger is being employed. What matters is “how fast” and “how wide.” The method of producing the vibrato may be changed from note to note or even on the same note. If the speed and width of the vibrato remain the same, it should be possible to change in mid-note from arm to wrist or from wrist to arm without a noticeable change in the sound.
When I play (even when I practice) I give no thought to whether I am using wrist or arm. I think only of the kind of sound I want—the kind of mood, color, and intensity, and whether the phrase is growing or relaxing. The method of producing the vibrato (wrist or arm) on any given note happens automatically and without any awareness on my part. If you were to ask me, after I had just played a phrase, which type of vibrato I had used on a given note, I would probably not have the slightest idea. I believe that this is as it should be. When one performs, one should be concerned with music, not mechanics.
Of course, to reach this stage, one must learn to vibrate with the wrist and with the arm, learn to control the speed and width in both cases, and practice to increase the speed and/or the width. I encourage most of my students to learn both types of vibrato. Usually they come to me with a definite inclination for one or the other, and, I must admit, they usually leave me with that same inclination. That’s fine! What they are doing is natural for them and enables them to sound their best. Some exceptional students actually do develop both kinds of vibrato. Some actually come to me with both kinds (although some of them do not realize it). At any rate, I try to develop an arm vibrato to go with a natural wrist vibrato and a wrist vibrato to augment a natural arm vibrato. I do not discourage the natural vibrato and I do not try to get the student to change to the other type.
Most of the time this sort of thing happens: A student will come to me with an arm vibrato that is stiff and tight. I will explain and demonstrate both types of vibrato and give him material to practice and develop both types. I will encourage him to develop a wrist vibrato as well as to improve his arm vibrato. He may or may not develop a useful wrist vibrato, but, even if he doesn’t, he usually winds up with a much freer, more relaxed, more versatile arm vibrato; and from working on the wrist vibrato, he will usually develop a relaxed wrist joint, which adds a dimension to the arm vibrato, if nothing more.
Similarly, the student with the wrist vibrato is encouraged to develop an arm vibrato, as well as to improve his wrist vibrato. He may gain an arm vibrato or he may feel much more comfortable with his natural wrist vibrato. What often happens is that he learns to use the arm with the fourth finger and/or in the upper positions, where the wrist is so bent that it can hardly be used.
Lots of good may be accomplished by encouraging both types of vibrato. In any case, no harm can be done as long as the student is encouraged to keep and improve his natural vibrato.
I would like to make this personal request to viola teachers: If you continue to teach a student beyond the beginning years, modify some of the things that you taught him initially. Explain to him why you taught him certain things at first and why you are now suggesting some refinements and exceptions. Tell him why you had to teach him that water seeks its own level, and show him why you now have to teach him about capillary attraction.