Voice production in singing and speaking, based on scientific principles

by Wesley Mills

Much discussion has taken place from time to time as to the nature of the larynx as a musical instrument, some being inclined to regard it as most closely allied to a stringed instrument, others to a wind-instrument. It has obviously points of resemblance to both, but the most recent researches make it clearer than ever that it is neither one nor the other, strictly speaking, but that it stands in a class by itself. It is, however, helpful, in considering many questions, to bear in mind its resemblances to both wind and stringed instruments. The vocal bands are not wholly free throughout their length, like the strings of a violin, nor do they bear any great resemblance to the reed of such an instrument as the clarinet, but as in the latter the force causing the vibrations is a blast of air. We have already pointed out that the vocal bands are set into vibration solely by the expiratory blast of air.

THE LARYNGOSCOPE.

The distinguished physiologist Johannes Müller demonstrated the working of the larynx by special experiments. He fixed into the windpipe a bellows, and showed, in the dead larynx, of course, that the blast from this source could cause the vocal bands to vibrate and thus produce sounds, which by varying the strength of the force, etc., were made to vary in pitch.

While such experiments indicate the essential principles of a possible voice-production, as the conditions in life were not and could not be fully met these results were rather suggestive than demonstrative of Nature's methods. These investigations served a good purpose, but they were manifestly inadequate, and this was felt by one thoughtful vocal teacher so keenly that he pondered much on the subject, in the hope of finding a method of observing the larynx during actual phonation. To this distinguished teacher, Manuel Garcia, belongs the honor of inventing the means of observing the vocal bands in action. This was accomplished in 1854, and, soon after, Garcia read an account of his observations to the Royal Society of London; and though much in this paper required correction by subsequent observations, it remains to this day the foundation of our knowledge of the action of the larynx in voice-production.

Fig. 38 (Bosworth). Intended to illustrate the optical principles involved and the practical method of carrying out laryngoscopic examination. The dotted lines show the paths of the light-rays.

As usually employed, the laryngoscope consists of two mirrors, the head-mirror, so called because it is usually attached to the forehead by an elastic band, and the throat-mirror, which is placed in the back part of the mouth cavity. The purpose of the head-mirror is to reflect the light that reaches it from a lamp or other source of illumination into the mouth cavity so perfectly that not only the back of the mouth, etc., but the larynx itself may be well lighted up; but inasmuch as this illumination may be accomplished, under favorable circumstances, by direct sunlight, the head-mirror is, though mostly indispensable, not an absolutely essential part of the laryngoscope. There is, indeed, one advantage in the use of direct sunlight, in that the color of the parts seen remains more nearly normal. Lamplight tends, because of its yellow color, to make parts seem rather of a deeper red than they actually are; but this to the practised observer, always using the same source of illumination, is not a serious matter—his standards of comparison remain the same. Moreover, this objection does not apply equally to electric light, now so much used.

Fig. 39. This illustration is meant to show more especially the relative position of observer and observed. The observer, on the right, is wearing the head-mirror, while two throat-mirrors seem to be in position—in reality, the same mirror in two different positions. One is placed so as to reflect the picture of the nasal chambers, especially their hinder portion. The walls of the nose, etc., may for the purposes of this illustration be considered transparent, so that the scroll (turbinated) bones, etc., come into view. The tongue is protruded. The light, not seen in this figure, is usually placed on the left of the subject, as in [Fig. 38].

It being a fundamental law of light that the angle of reflection and the angle of incidence correspond—are, in fact, the same—it was necessary that the throat-mirror should be set at an angle to its stem, so that the light passing up by reflection from the larynx should, when striking on the surface of this plane throat-mirror, be reflected outward in a straight line to the eye, which must be in the same horizontal plane with it. This and all the other facts and principles involved can only be understood by a careful inspection of the accompanying figures, which it is hoped will make the subject plain. The throat-mirror is none other than the mouth-mirror of the dentists, and in use by them before Garcia discovered how it might be employed to throw light on the larynx, in a double sense.