The first volume of Evolution of Expression deals with each composition
as a whole in its various aspects. The second volume deals with the
_Parts_ of the composition considered as wholes. When the mind in its
development in expression is able to deal definitely with each separate
part of the discourse by itself, it is revealed by slides in the voice,
each new and distinct thought causes the voice to give a new and
distinctive slide. I am using the word “Slide” in the same sense in
which the word “inflection” is often used.
Slide is the continuation of the voice from one pitch to another. An
ascending slide is one in which the voice is continued from a lower to a
higher pitch. A downward or falling slide is one in which the voice is
continued from a certain pitch to a lower one. The rising circumflex is
one in which the voice starts on a certain pitch, continues to a lower,
and then rises to a higher. In the falling circumflex the voice starts
on a certain pitch, rises to a higher one, and then falls to a lower
without ceasing.
The physiological condition of the vocal organs which produces Slide is
determined entirely by the tension of the vocal cords. With the same
degree of tension and power of stroke, a long string vibrates more
slowly than a short one.
If the vocal cords are sound and healthy we are perfectly unconscious of
their existence. We cannot teach the vocal cords how much to contract or
lengthen when giving a certain pitch. We are compelled to leave it to
the mind not only to hear the pitch, but to impel the proper contraction
of the vocal cords in its production.
If the mind can control unconsciously the contraction of the muscles of
the larynx, it can as easily control the tongue, the size of the throat,
the pectoral muscles, and, in short, all the muscles that influence the
voice.