the nasal cavity, including the sinuses,
suggests itself. Of what use is the nasal passage as a cavity of
resonance if, in order to prevent a nasal quality of tone, the passage
during voice-emission is shut off by the action of the soft palate, or
by the combined action of the soft palate, uvula and tongue? The answer
is, first, that it is not always to be closed off, because there are
times when a slightly nasal timbre in voice is desirable; secondly,
that even when the nasal cavity is shut off, the hard palate being
not only the roof of the mouth but also the floor of the nose, its
vibrations are communicated to the nasal cavity, but not directly enough
to give a disagreeable nasal quality to the voice.

From this survey it will be seen that the cavities of resonance along
the vocal tract may be divided into such parts as are solid, pliable
and movable. The solid parts are sharply resonant; they are, _par
excellence_, the resonators in voice-production; while a pliable part,
like the pharynx, although resonant in a less degree, is valuable in
adjusting structural shape to every condition that arises; and the most
movable parts of all, the tongue and the lips, probably wholly devoid
of resonance, have their great roles to play in effecting what may be
called wholesale changes in the size and shape of the mouth-cavity,
which could not be brought about by any other agencies less mobile.
The roof of the mouth, the teeth, the hard gums, the cones of the nasal
passage, and the sinuses are the solid portions of the cavities of
resonance. When Svengali gazed into Trilby's mouth and exclaimed,
"Himmel, what a roof!" he spoke from the depths of vocal knowledge.
For a highly arched mouth roof, especially if the tone enters the mouth
cavity from a wide, well-rounded pharynx, is of great value to the
singer. So is a fine, shapely, regular set of teeth, especially as
regards the upper front teeth, behind which the vibrations appear to
centre in so called "forward production." Cautiously brought into play,
the posterior nasal passage assists, with its resonance, the head tones
of the female voice and the upper range of male voices; but care must
be taken not to carry the tone up into the nose and thus give it a nasal
quality.

Some writers class the walls of the pharynx with the solid parts of the
vocal tract. But the walls of the pharynx are pliable, as already has
been pointed out, together with the admirable results to be derive