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CONCEPTS OF PRONATION |
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The following interesting summaries of the pitch regulating process are quoted from Negus [418]:
a) "Experiment shows that the pitch of vocal sounds is determined by the larynx (itself) and is not altered by the various pharyngeal, oral, and nasal resonators." [p. 439]
b) "It has been observed that the vocal cord (cadaveric) of an adult man is 23 mm. in length, and that this length can be increased (mechanically) to 27.5," a difference of 4.5 mm. "This is a big range of movement to expect of the arytenoid cartilage, while such a movement —if it occurred—would require the exertion of a force much greater than that possessed by the small postici [crico-arytenoid] muscles. . . . These reasons appear to me to be sufficient evidence on which to state that stretching of vocal cords is an . . . extremely unlikely factor in the normal [pitch-regulating] mechanism of man. . . . Some other factor must be discovered and this, I think, is to be found in the capability of contraction" within the vocal cords [thyro-arytenoid muscles] themselves, [p. 373]
c) Therefore, "changes of pitch are not produced by stretching of the vocal cords. Changes of pitch are determined by the degree of contraction of the thyro-arytenoid muscles, whereby the degree of elasticity of the margins of the glottis can be regulated." [p. 439]
d) "The other muscles of the larynx play a secondary part in holding the arytenoid cartilages in a suitable position." [p. 376]
e) "The conclusion—corroborated on many occasions—is that if the larynx remains in the same condition as regards its vocal cords, increase of air pressure [also] raises the pitch." [p. 384]
f) "Therefore it is obvious that rises of pitch are attained by variations both of air pressure and of elasticity of the glottic margins. . . . In actual phonation the two are associated in such a way that slight increase of air pressure causes considerable rise of pitch, [p. 386 ff.]
Extrinsic mechanisms. The muscles and parts of the larynx that are not entirely contained within it, but extend from it to other parts of the body are referred to as extrinsic mechanisms, to distinguish them from intrinsic mechanisms that are included wholly within the larynx. In its function as a generator of vocal tone for singing, the larynx is not a fixture. It is freely movable and is suspended in the throat by means of flexible extrinsic muscles that connect it with the cranium, tongue, hyoid bone and jaw above, and with the breast bone (sternum) and shoulder bones (omos) below. [Edwards 158] The accepted latin and greek terms used to name such |
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