Moreover, the photographs show that the
vocal cords at the break from the lower to the upper register exhibit
characteristic changes.
[Illustration: Fig. 11]
[Description: Fig. 11.--Drawings after Dr. French's photographs in Sir
Felix Semon's lecture on the Voice, (1) Appearance of vocal cords of
contralto singer when singing F# to D; it will be observed that the cords
increase in length with the rise of the pitch, presumably the whole cord is
vibrating, including the inner strand of the vocal muscle. At the break
from D to E (3 and 4) the cords suddenly become shorter and thicker;
presumably the inner portion of the vocal muscle (thyro-arytenoid) is
contracting strongly, permitting only the edge of the cord to vibrate. For
the next octave the cords are stretched longer and longer; this may be
explained by the increasing force of contraction of the tensor muscle
stretching the cords and the contained muscle, which is also contracted.]
When we desire to produce a particular vocal sound, a mental perception of
the sound, which is almost instinctive in a person with a musical ear,
awakens by association motor centres in the brain that preside over the
innervation currents necessary for the approximation and minute alterations
in the tensions of the vocal cords requisite for the production of a
particular note.
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