the act of inspiration (Fig. 3), are wide open so as to allow the free ingress of air, and even during ordinary expiration (Fig. 3) they remain sufficiently wide open not to hamper the freedom of respiration. When the voice is used, however, the lungs having obtained the necessary supply of air, the edges of the vocal cords are brought together (Fig. 1), and, as the air is forced through them by the contraction of the lungs, they are set up in vibration, thus producing the voice.
Two vertical sections of the larynx are shown in Figs. 4 and 5 (after Merkel), the former 
Fig. 3. Vocal Cords During Expiration. showing the vocal cords (1, 2) in the lower register, and the latter the vocal cords (1, 2) in the high register. In both Figs., 5 and 6 represent the pockets or ventricles of the larynx, and 3 and 4, the ventricular bands, sometimes called the false vocal cords. Figs. 7 and 8 show a section of a cartilage of the larynx.
The voice, like other sounds, varies in pitch, loudness and timbre. The pitch is due to the tension of the vocal cords, the process, however, being somewhat more complicated than in a violin in which there are several strings. There being but one pair of vocal cords in the larynx, the tones are produced, first, by tightening the vocal cords, and, when the limit has been reached, so that a greater degree of tension would be injurious to the vocal cords and the muscles which control them, there is set up a different form of vibration known as the change of register. This subject of the register is somewhat complicated,
but it will be better understood if we suppose that the difference between a low and a high register is due to the fact that in the latter a shorter portion of the vocal cords is set into vibration.
The bass, for instance, produces his lower tones by increasing the tension of the vocal cords until B flat (International Pitch) is reached when he changes his register, obtaining his remaining upper tones by contracting the vocal cords in this register. The untrained singer, however, not understanding this change of register, may attempt to reach the upper tones by simply increasing the tension in the lower
