Allusion must be made to the danger of those engaged in mathematical and physical investigations applying their conclusions in too rigid a manner to the animal body. It was held till recently that the pitch of a vocal tone was determined solely by the number of vibrations of the vocal bands, as if they acted like the strings of a violin or the reed of a clarinet, while the resonance-chambers were thought to simply take up these vibrations and determine nothing but the quality of tone; they were believed not to have any influence on pitch. Against this view the author long ago demurred. To Prof. Scripture, however, belongs the credit of demonstrating that the resonance-chambers determine pitch also. It seems probable that the vocal bands so beat the air within the resonance-chambers as to determine the rate of vibration of the air of these cavities, and so the pitch of the tone produced. These chambers not having rigid walls, one can the better understand that the tension of these parts may not only be different in individuals, but vary in the same person from time to time, according to the condition of his health, etc. Herein we find another source of explanation of variations in the voice. All these considerations make the resonance-chambers more important than ever, so that there is greater objection to speaking of the larynx as the vocal organ than we were aware of before these investigations were undertaken.
SUMMARY.
Without a resonator, which may be solid or hollow, the sound made by a reed or tense string is feeble. That the mouth can act as a resonator may be proved by holding a vibrating tuning-fork of suitable pitch before this chamber when open.
The resonating chambers of importance are supra-glottic. Of these the "mouth" including all as far back as the pharynx and the nasal chambers are the principal. These two main cavities are separated from each other by the hard palate, which is a bony floor, covered with mucous membrane, as are all the parts of the resonance-chambers. The hard palate extends horizontally from the gums backward, and is continued as the soft palate. The latter is a muscular and therefore movable curtain that divides, with varying degrees of completeness, the mouth (in the narrower sense) from the pharynx and naso-pharynx—i.e., the space back of the soft palate and the posterior nares (back nostrils) respectively. By the elevation of the back of the tongue and the lowering of the soft palate as when one speaks nasally, the mouth proper is largely shut off from the nasal chambers, so that the breath must be directed through the nose. "Cleft palate" also connects undesirably the mouth and nasal chambers. The tonsils lie between two folds, the pillars of the fauces, connected with the soft palate. When normal in size the tonsils should scarcely extend beyond these folds. The uvula is the central lower tip of the soft palate. The nasal chambers are divided by a central bony and cartilaginous partition, the septum nasi, but are further encroached upon, on each side, by three scroll-like (turbinated) bones. The tongue is composed of several muscles, which explains why its movements may be so complicated and delicate. The mouth cavity is bounded in front by the gums, teeth, and lips.
The form and, to some extent, possibly; the size of the resonance-chambers determine the quality of the tone produced in speaking and singing. The shape and size of the mouth can be made to vary by the soft palate and lips, but chiefly by the tongue, so that the movements of the latter, especially, cannot be too well studied.
It was formerly considered that pitch was determined solely by the rate of vibration of the vocal bands; though the author opposed this view as rigidly applied. Very recently Prof. Scripture, by the use of new methods, has shown that the supra-glottic chambers cannot be correctly likened to a resonator with rigid walls. It is held that the vocal bands give a number of sudden shocks to the air in the resonators, so that, in a sense, the resonance-chambers determine both the pitch and the quality of the tone; and as the tension of the resonators varies with both the physical and psychical condition of the individual, variations in tone-production, more especially as to quality, can now be the better understood. According to this view these chambers are not properly resonators but sounding cavities.
The reader's attention is particularly drawn to the new views of the method of action of the vocal bands, etc., referred to on this page. Since the above was written, such views have become more widely known, and it is hoped that as they are very radical they may be established by other methods.