Interesting thread. Allow me to weigh in.
In singers, vibrato is primarily pitch modulation. Any amplitude modulation
is a secondary effect. You can check this by recording singers on a digital
program such as MOTU's Digital Performer, and analyzing the sound bites. Or
you can slow up the audio (either digitally, or with a slowed down tape
recorder), and hear distinctly the separate tones representing the vibrato.
I've been a singer all my life, and the following is my understanding of the
vocal mechanism involved: The vibrato is produced by a relaxation of the
muscles controlling the vocal cords, which relaxation allows air to pulsate,
unhindered, through the vocal chords, up and out of the head. You can check
this by singing a sustained "ah" in a normal head position, then lowering
your chin all the way down until it rests on your chest. You'll hear the
constriction of the tone, and ultimately the elimination of the vibrato, as
more and more air flow is restricted. I also believe there may be an
influence of sonic overtones. When the vocal-head alignment is pinched, the
overtones of the sound literally interfere with each other and squelch
production.
Although produced by air, I don't think of vibrato as a diapragmatic action.
I can increase or decrease my vibrato without any mental adjustment except
in the upper part of the vocal mechanism. On the other hand, the volume and
pressure of air is a factor. If the singer is over-blowing, i.e., sending
too much air into the voice box, the sound is husky and is called by vocal
teachers "hyper-phonation;" if the volume of air is insufficient
("Hypo-phonation"), the tone is flaccid and typically under pitch.
"Wobble" refers to a flaccidity of the muscles that control the vocal cords,
such that the fluctuations in pitch and speed of the fluctuations (i.e., the
time interval between the two intervals constituting the limits of the
vibrato) are wider and slower, respectively. As we grow old, flaccidity of
the muscles increases (heh-heh!) and thus wobble is a greater problem with
senior adult choirs than it is with the youth choir.
Voice teachers do teach vibrato, generally, but not so much to create an
"operatic" effect, as it is to allow maximum vocal freedom (i.e.,
unrestricted passage of air through the body) thus increasing volume and
resonance of the tone, while preserving the vocal instrument. In choral
singing with elder choirs, where "wobble" becomes a problem, one of the
fixes is to suggest that the choir "add more air" to the sound. In that
instance, diaphragmatic action and control may be appropriate.
For those interested, a good book on the subject of singing and vibrato,
wobble, etc., is "The Diagnosis and Correction Of Vocal Faults" by William
McKinney, the late Dean of Music at Southwestern Baptist Theological
Seminary in Fort Worth. The book was used as the text for Dean McKinney's
class in Vocal Pedagogy. Sorry, I don't recall the publisher.
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> Date: Fri, 21 Feb 2003 12:00:20 -0600
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> Subject: Finale digest, Vol 1 #430 - 16 msgs
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