s of the face--in fact
pretty much every hollow space in the head, every space that will
resound in response to vibration and assist in multiplying it. Moreover,
the cavities of resonance by their differences in shape in different
individuals determine the timbre or quality of individual voices. The
chest, although situated below the larynx, is a resonance cavity of
voice. In fact, in a certain register its vibration is felt so
distinctly that we speak of these notes as being sung in the "chest
register," which, so far as it implies that the tones are produced in
the chest, is a misnomer. The same is true of "head register," in which
vibration is felt in the head where, however, it is needless to say,
the "head tones" do not originate.

Expiration--breath-emission--is the motor function of the vocal organs;
and there are two other physical functions of the organs--vibratory and
resonant.

Added to these is the sensory function, to which I attach great
importance; and I call it a psychological function because it acts
through the nerves upon the physical organs of voice. Without it the
three physical functions--motor, vibratory and resonant combined--would
remain ineffectual. They could generate voice, but it would be voice
lacking those higher qualities that are summed up in the word
"artistic." It would be a physical, not an art product, a product
generated by the body without the cooperation of the mind or soul. When
it is considered that the larynx, in which the vocal cords are situated,
is permeated by a network of muscles through which it is capable of some
16,000 adjustments and readjustments of shape, all of them pertinent to
voice-production, and that the same thing also is true of the pliable
portions of the resonance cavities; that these muscles act in response
to an even finer network of nervous filament; and that the constant
shaping and reshaping of various parts of the vocal tract during
voice-emission is directed by messages from the mind, soul, or art-sense
of the singer, messages which travel via nerve to muscle--the only route
by which they can travel--it becomes possible to appreciate the
importance of the sensory or psychological function which, I hold,
should be added to the purely physical ones of motor, vibration and
resonance. For by it these functions are enlisted in the service of
art and made immediately and exquisitely responsive to the emotional
exaltation of music and song. Nor are these