enlargement of the oral cavity, especially its back part; and smoothness is
the result of the free vibration of the vocal chords, while resonance is
produced by the proper expansion of the chest.

MODULATION. This has reference, not to the qualities of the voice itself,
but to its management in delivery. It includes those modifications and
variations which are requisite for the expression of thoughts and feelings,
and are therefore denominated by some elocutionists, the elements of
expression, in distinction from the elements of utterance, which we have
already considered under the preceding heads. The principal expressive
modifications of the voice, are pitch, force, rate, pause, and infection.
The voice should be exercised on these elements separately, till each can
be produced in all its varieties and degrees. The middle pitch, or
key-note, is that of common discourse, but by practice it may be rendered
effective in public speaking. Neglect to cultivate and develop the power of
speaking on this key, often leads speakers to adopt the high, shouting
note, which is heard so commonly, and with so much disapprobation, at
exhibitions of declamation. Every one can speak on a high key, although
without training few can do it pleasingly; but command over the low notes
of the voice is a rare accomplishment, and an unequivocal characteristic of
the finished speaker. It is well to pay some attention to the very high and
very low notes, not so much for their own utility in public speaking as for
the purpose of giving strength and firmness to the notes which are
intermediate between the natural pitch and either extreme, and which are
designated as simply high and low, without any qualifying term. After
accustoming the ear and voice to the different notes, the student should
learn to make sudden transitions from one key to another.

FORCE. The principal degrees of force requiring attention, are three: the
moderate, the declamatory, and the impassioned. The degrees lower than