of the mechanical law of tone-production.

Considered as a mechanical process, tone-production occurs when the
energy exerted by the expiratory muscles, in their contraction, is
converted into energy of motion of the vocal cords.[8] In other words,
tone-production is an example of the transformation of energy. The law
of the transformation and conservation of energy must therefore apply to
this operation. This law is stated as follows: "Energy may be
transformed from any of its forms to any other form. When energy is thus
transformed the quantity of energy in the resulting form or forms is
equal to the quantity of energy in the original form."

[Note 8: This exposition of the mechanical principle of
tone-production is intended to be graphic, rather than strictly
technical. For the sake of simplicity, that portion of the expiratory
energy expended in friction against the throat walls, tongue, cheeks,
etc., is disregarded, as well as that expended in propelling the air out
of the mouth, in displacing the same quantity of external air, etc.]

The mechanical operation of tone-production comprises the following
transformations of energy: First, the energy exerted in the contraction
of the expiratory muscles is converted into energy of condensation or
elasticity of the air in the lungs and trachea. Second, this energy of
condensation of the air is converted into energy of motion of the vocal
cords. In other words, the expiratory energy is transformed into energy
of motion.

One objection, at first sight very serious, may be offered against this
statement: the amount of strength exerted in the contractions of the
breath muscles seems many times greater than is accounted for in the
motion of the vocal cords. The movements of the vocal cords are so
slight as to be observable only with the aid of a specially devised
apparatus, the stroboscope. Can all the expiratory force expended in
tone-production show such a small result? This apparent objection is
found to be groundless in view of the application in this operation of
Pascal's law. As this topic was fully treated in Chapter II of Part II,
no further explanation is required here.

The erroneous idea of vocal mechanics involved in the doctrine of
breath-control is now fully exposed. Tone can be produced only when the
expired air exerts a pressure on the vocal cords. There is no necessity
for any conscious or voluntary check on the expiration. The energy of
the expiration is