.

There should be some good physiological reason for the habitual recourse
to the strident chest-voice so common with boys, and nearly as usual
with girls. And there is a good reason. It is _lack of rigidity in the
voice-box or larynx_. Its cartilages harden slowly, and even just before
the age of puberty the larynx falls far short of the firmness and
rigidity of structure, that characterize the organ in adult life. It is
physically very difficult for the adult to force the chest-voice beyond
its natural limits, which become fixed when full maturity of bodily
development is reached, but the child, whose laryngeal cartilages are
far more flexible, and move toward and upon each other with greater
freedom, can force the chest-voice up with great ease. The altitude of
pitch which is attained before breaking into the thin register is with
young children regulated by the amount of muscular exertion they put
forth. Even up to the change of voice, boys can often force the thick
register several notes higher than women sopranos.

It must be borne in mind that the thick voice is produced by the full,
free vibrations of the vocal bands in their entire length, breadth and
thickness.

Imagine children six years of age carrying tones formed in this manner
to the extreme limit of their voice; yet they do it. The tone of infant
classes in Sunday-schools, and the tone of the primary schools, as they
sing their morning hymns or songs for recreation, is produced in nine
hundred and ninety-nine cases out of a thousand in exactly the way set
forth. If the vocal bands of children were less elastic, if they were
composed of stronger fibres, and protected from undue exertion by firm
connecting cartilage; in short, if children were not children, such
forcing would not be possible. If it were not for the wonderful
recuperative power of childhood, serious effects would follow such vocal
habits.

We are now prepared to understand that common phenomenon of the
child-voice, termed the "movable break." Every public school teacher who
has had experience in teaching singing must be familiar with the meaning
of the term, though possibly unaware of it. Allusion has already been
made to the fact that, in primary grades, the thick quality, if
permitted, will be carried as high as the children sing, to

[Music: e'']

for example. If they are required to sing the higher tones lightly, then
the three or four tones, just below the pitch indicated,