he production of sound, may
be compared to an organ-pipe. The two vocal cords which act
simultaneously and are anatomically alike, when set in vibration by the
blast of air coming from the lungs, correspond to the reed of the
organ-pipe; the vibration of the cords, producing sound, which is
communicated to the air enclosed in the cavities of the chest and head.
Pitch of tone is determined by the rapidity of vibrations of the bands,
according to acoustical law, and the length, size, and tension of the
cords will determine the number of vibrations per second, _i.e._, their
rapidity.

Strength or loudness of tone is determined primarily by the width or
amplitude of the vibrations of the vocal membrane, and quality or timbre
is determined by the form of the vibration.

The infinitely varying anatomical divergencies in the form and structure
of the nasal, pharyngeal and throat cavities, and possibly the
composition of the vocal bands, modifies, in numberless ways, the
character of tone in speech or song. It is a fascinating topic, but must
be dismissed here with the remark that, as those anatomical differences
in structure are far less marked in children than in adults, their
voices are, in consequence, more alike in quality and strength. It takes
long, patient training to blend adult voices, but children's voices,
when properly used, are homogeneous in tone.

The voices of boys and girls, prior to the age of puberty, are alike.
The growth of the larynx, which in each is quite rapid up to the age of
six years, then, according to all authorities with which the writer is
conversant, ceases, and the vocal bands neither lengthen nor thicken, to
any appreciable extent, before the time of change of voice, which occurs
at the age of puberty.

It is scarcely possible, however, that the larynx literally remains
_unchanged_ through the period of the child's life, extending from the
age of six to fourteen or fifteen years. In point of fact, authorities
upon the subject refer only to the lack of growth and development in
_size_ of the larynx during the period; but _undoubtedly, during these
years, there is a constant gaining of firmness and strength, in both the
cartilages and their connecting membranes and muscles_. None of the
books written upon the voice have even mentioned this most important
fact. It bears with great significance upon questions relating to the
capacities of the child's voice at different ages, and explains that