This story starts about 15 years ago. At a chamber-music soirée in a private home, after playing and during the snacks served late in the night, one of the assistants, a neurologist, remarked that during the last years he was being consulted by a new clientele: People with nervous disorders who were assiduous visitors to discotheques, and fond of rock-music, the louder the better. Our doctor attributed the disorders to our subliminal coexistence with our pulse, our heart-beat, which in this case was attacked by a strong exterior pulse imposed on our own: Hence the protest of our nervous system. It ocurred to me that if we were indeed dependant, in some misterious way, on or own pulse, this could also be used to our advantage.
We are all aware that there are preconditions to an agreeable vibrato, such as what we call tapping on the strings with our left-hand fingers, letting the weight of the fingers fall on the string without pressure, just as a bag of potatoes would fall, somewhat squat but nothing else. But there were students that did tapping nicely yet did not start vibrato and evidently needed some help to get going. (In my experience, only 25% of all students start vibrating by their own. I am however against a muscular approach, moving each finger to and fro on the spot: This can develop into a robot-like, unpersonal vibrato. Maybe an exception can be made with the little finger, but this muscular excercise can be done with a pencil, or with your own right hand for support).
What I did to start the process was putting my own hand in place of the fingerboard, asking the student to massage an imaginary spot where I just had received an injection. Everybody responded perfectly to this, by doing a vibrato-like motion to do the job. However, when asked to do the same thing on the instrument, the result was far less satisfactory. A pretty wobbly, irregular vibrato was audible. At this stage the student would be asked to go home and think about it, and have several attempts towards improving. After a week or two, the first resistance to new sensations having been overcome, I then started on my scheme related to the neurological phenomenon mentioned above.
With a half-note melody, for beginners, such as Sevcik op 2 no 4, or a two-octave scale, the student was asked to play this for 2-3 minutes each day with the metronome ticking away all the time, to start with at 80 beats per minute, four beats per half note,one half-note per bow. After a few weeks, the tempo would be changed to a range between 60 and 96 beats per minute, and the bowing pattern altered for longer slurs (see diagram).
An average student would develop a very reasonable, regular, well-sounding vibrato as soon as three months after starting on this discipline. It appears that our organism wants to conform to the artificial heart-beat of the metronome, and supply by its own exact multiples of the given tempo. The metronome does not beat rhythm in this case but acts as pulse, and that is a different matter alltogether. (I only resort to the metronome for rhythm if the student has trouble with beat, or to clarify a very complicated score; otherwise I like to rely on the student's own rhythmic ability).
Most students will stop vibrating just before the next note is to be stopped. This must be pointed out to them: They should vibrate until the next finger "falls" on the next note. A few reminders during the first weeks of work will do.
If any of the teachers reading this has access to an oscilloscope, it is easy to verify the results: You just feed one single note through a microphone, and adjust the beat of the oscilloscope to the one of the metronome. You will be surprised how after a few moments an average student will produce a remarkably even sinus-wave with his vibrato, and that crests or valleys will show the multiple of the given tempo, at a regular frecuency. It is precisely this regularity which carries tone.
The remarkable result of the method is however that in some mysterious way the personality of the student has stayed intact: Good carrying tone is achieved, but different students still sound dissimilar and if you know them well you will recognise their inner voice and way of expressing themselves.
As you well know, vibrato very much depends on age, muscle, built and stamina of the student. Furthermore, there will evidently be a big difference between talented and untalented students. But getting a pleasing sound out of their instruments will very much stimulate all of them, and make the up-hill study a little more agreeable.
After fifteen years of using this method I am fully satisfied, and it was only upon the insistence of a colleague of mine - another independant teacher younger than I who uses some of my students in a youth orchestra - who asked me what I did to get such a nice sound from them, that I decided to talk about this and share it with you and others. I am 75 years old and at the end of my career, but it would give me a lot of satisfaction to hear whether the method worked out as satisfactorily with others as it did with me.
PS.: Only a few months ago I was told by an obstetrician that he was not at all surprised that this method worked: Hyper-active fetuses or babies are calmed down by hearing their heart-beat, softly amplified. And how often do we see babies stop crying when held tight to their father's or mother's heart, skin to skin. We just forget about our pulse, but it is always there. Let us make the best of it! .
John Krakenberger's web site: http://www.geocities.com/krakenberger/