When the mind has separated one thought distinctly from the other main
thoughts of the subject, and has become intensely attracted to it with a
special desire to communicate it as distinct from the others to the
minds of the hearers, all the muscles will act in a way to produce Vital
Slide.
This principle of Vital Slide may be illustrated by “The Forging of the
Anchor.” When the mind becomes aroused with this selection there is in
the quality of the voice something of the spirit of the fife, the drum,
and the military movement.
Swing in your strokes in order; let hand and foot keep time;
Your blows make music sweeter far than any steeple’s chime;
But while ye swing your sledges, sing, and let the burden be,
The anchor is the royal king, and royal craftsmen we.
It is the energy of the mind which causes the energy of the muscles. The
energy of the contraction of the muscles causes the report of that
energy in the voice.
Under Vital Slide we consider the relation of the muscles of respiration
to the vocal cords. There are two sets of respiratory muscles, the
muscles of inspiration and the muscles of expiration. If the thought
requires for expression an increase of vitality in the voice, the
muscles of expiration contract more strongly, thus giving greater
density to the air in the lungs. The air, being an elastic substance, in
seeking egress or relief presses strongly against the vocal cords, which
are forced apart with such energy as to give an expression of greater
vitality to the tone produced.
It is not necessary to exert the will consciously on the different
muscles which act upon the vocal organs. It is not necessary to call the
roll and say, “Triangularis sterni, Diaphragm, Abdominal muscles,
Intercostals, contract! Abdominal muscles, you must contract only just
enough to overcome the contraction of the diaphragm. Now, all
together—one, two, three, contract!” One should not think anything
about these muscles. He should be no more conscious of their action than
he is of the beating of his heart.