"Usually, therefore, at the note C♯
[LISTEN] in the female voice, and A, B♭
[LISTEN] in the male voice, the vocal ligaments alone act in forming the sound, and are throughout the register moved by large, loose, full vibrations. But the instant the vocal ligaments are deprived of the assistance of the pyramids they relax, and appear longer than at the last tone produced by that aid. But with every higher tone they appear again to be stretched shorter and more powerfully up to F, F♯
[LISTEN] the natural transition from the thick to the thin register, as well in the male as in the female. The voicebox is perceptibly lower in all the tones of the thick register than in quiet breathing."
I confess my inability to understand how the vocal ligaments can get longer by relaxing and shorter by stretching. But apart from this I assert that there is no relaxing of the vocal ligaments at the break between the Lower Thick and the Upper Thick at all. This is clearly proved by the ring-shield aperture, which would open immediately if such were the case. I also doubt whether the action or inaction of the pyramids determines the break between the Lower Thick and the Upper Thick, as they are cartilages—i.e., pieces of gristle—and cannot, therefore, by any vibrations of their own assist in the production of tone. The tension of the vocal ligaments increases as we sing up the scale until the ring-shield aperture has quite disappeared. But while it remains so closed, and without the vocal ligaments being any further stretched, we can yet sing higher still. The gradations of tone are now no longer formed by the action of the ring-shield muscles (see p. [34]), but by the shield-pyramid muscles which press the vocal ligaments more and more closely together, until at last scarcely any trace of a slit remains between them. Another result of this action of the shield-pyramid muscles must also be to narrow the space below the vocal chink, which, as we know from the experiments of J. Müller, has the effect of raising the pitch of tones. I think it very likely, therefore, that the change from the lower to the upper thick is really brought about by the shield-pyramid muscles coming into play after the ring-shield muscles have done their share.
THE THIN REGISTER.
"All the tones of the thin register are produced by vibrations only of the fine, inner, slender edges of the vocal ligaments. In this action the vocal ligaments are not so near together, but allow of a fine linear space between them, and the pocket ligaments are pressed further back than in the production of the tones of the thick register. The rest of the action of the glottis is, however, entirely the same. With the beginning of the thin register at F♯