THE PHARYNX
The pharynx extends from the larynx to the nasal cavity. The size of the opening into the nasal chamber is controlled by the soft palate and is frequently entirely closed. The size of the pharynx is varied by the contraction and relaxation of the circular muscles in its tissue; when swallowing its walls are in contact. The pharynx acts as does the expanding tube of brass instruments. It increases the force and depth of the tone waves. The wider the pharynx is opened, without constraint, the fuller the resonance and the better the tone.
THE UNDER JAW
The under jaw furnishes attachment for the muscles of the tongue and hyoid or tongue bone. It also controls, owing to the connections of the larynx with the hyoid bone, the muscles that fix the position of the larynx.
The pterygoid muscles, which move the under jaw forward and backward, do not connect with the larynx, so their action does not compress that organ or in any way impede the action of the vocal apparatus. A relaxed under jaw allows freer action of the vocal cords and ampler resonance. The under jaw should drop little by little as the voice ascends the scale, thus opening the mouth slightly wider with each rise in the pitch of the tone. In ascending the scale it is well to open the throat a little wider as you ascend. The delivery will be much easier, and the tone produced will be much better. At the highest pitch of the voice the mouth should open to its full width. At the same time care must be taken not to draw the corners of the mouth back, as in smiling, because this lessens the resonance of the tone and gives it a flat sound.
The under jaw must have considerable latitude of motion in pronunciation, but by all means avoid chewing of the words and cutting off words by closing the jaw instead of finishing them by the use of the proper articulating organs, which are the tongue and lips.
THE SOFT PALATE
Writers on the voice have almost universally claimed that the principal office of the soft palate is to shut off the nasal and head cavities from the throat, and to force the column of vibrations out through the mouth, thus allowing none, or at most a very small part, to pass into the nasal passages.
This contention implies that the vibrations are imparted to the upper cavities, if at all, through the walls of the palate itself, and not through an opening behind the palate. This is entirely at variance with the facts as verified by my own experience and observation and the observation of others who are expert specialists. The true office of the soft palate is to modify the opening into the nose and thus attune the resonant cavities to the pitch and timbre of the note given by the vocal cords and pharynx. To develop the vowel sounds, the soft palate should be drawn forward, allowing a free passage into the nose; it should be closed only to form the consonants which require a forcible expulsion of breath from the mouth.
The uvula, the pendulous tip of the soft palate, serves as a valve to more accurately adjust the opening behind the soft palate to the pitch of the voice. In producing a low tone the soft palate is relaxed and hangs low down and far forward. As the voice ascends the scale the tension of the soft palate is increased and it is elevated and the uvula shortened, thus decreasing the opening behind the palate, but never closing it. In fact the larger the opening that can be maintained, the broader and better the tone. The author was himself unable fully to appreciate this until he had become able to sense the position of the soft palate during vocalization.