(the mouth) has for its roof the soft palate and the hard palate, the
tongue for its floor, and cheeks, lips, jaw, and teeth for its walls. The
interior dimensions of this portion of the resonator can be greatly
modified by movements of the jaw, the soft palate, and the tongue, while
the shape and form of its orifice is modified by the lips.

There are accessory resonator cavities, and the most important of these is
the nose; its cavity is entirely enclosed in bone and cartilage,
consequently it is immovable; this cavity may or may not be closed to the
sonorous waves by the elevation of the soft palate. When the mouth is
closed, as in the production of the consonant m, e.g. in singing _me_, a
nasal quality is imparted to the voice, and if a mirror be placed under the
nostrils it will be seen by the vapour on it that the sound waves have
issued from the nose; consequently the nasal portion of the resonator has
imparted its characteristic quality to the sound. The air sinuses in the
upper jaws, frontal bones, and sphenoid bones act as accessory resonators;
likewise the bronchi, windpipe, and lungs; but all these are of lesser
importance compared with the principal resonating chamber of the mouth and
throat. If the mouth be closed and a tune be hummed the whole of the
resonating chambers are in action, and the sound being emitted from the
nose the nasal quality is especially marked. But no sound waves are
produced unless the air finds an exit; thus a tune cannot be hummed if both
mouth and nostrils are closed.

From the description that I have given above, it will be observed that the
mouth, controlled by the movements of the jaw, tongue, and lips, is best
adapted for the purpose of articulate speech; and that the throat, which is
less actively movable and contains the vocal cords, must have greater
influence on the sound vibrations without participating in the articulation
of words. While the vocal cords serve the purpose of the reed, the