While, however, the importance of the vocal cords in tone-production has been overestimated, I should be going to the opposite extreme if I limited their importance to their function as the lips of the glottis. Not only are they lips, but vibrating lips, their vibrations, however, requiring enforcement through the sympathetic vibrations which they generate within the cup of the larynx and in the cavities above. As lips, the vocal cords shape the air-column as it enters the larynx, to the required note; as vibrating lips--set into vibration by the very air-column to which they have given shape--they start the vibrations essential to pitch and pass them along into the cup of the larynx, which also has shaped itself to the note and where gyration and friction begin to reinforce the vibrations started by the cords. What is true of the cup also is true of the resonance-cavities. In other words, the entire vocal tract, from cords to lips, shapes and reshapes itself with reference to the tone that is to be produced, and what thus goes on above the vibrating cords coöperates to produce the effect formerly attributed to the cords alone. The fact that the cup of the larynx subtly changes its shape for each tone produced, makes the hitherto obscure subject of registers of the voice, which many writers have written _around_ but none _about_, perfectly clear. The cup assumes what may be called a generic shape for each register, and then goes through subtle adjustments of shape for the different notes within each register. But this is a subject to be taken up in detail later. The reader now will understand why at different points in this chapter I have emphasized the fact that the larynx as a whole and throughout all its parts is capable of numerous adjustments in shape, and that the same is true of the resonance-cavities. The vocal tract of an accomplished singer is capable of as many adjustments as a sensitive face is of changes in expression. This phenomenon is the vocal tract making ready to generate, vitalize and emit the tone suggested by the mind--mind pressing the button, the physical organs of voice-production doing the rest. CHAPTER VI PITCH AND SYMPATHETIC VIBRATION