The Vocal Instrument
THE VOCAL INSTRUMENT
The production of voice in speech is a habit and, like most habits, is generally given little thought. Nevertheless the making of vocal sounds requires a mechanism of an intricate and highly developed character. In fact, the voice is without doubt the most efficient sound producer in existence. Since some of you may not have thought of your voice in such light, it may be well to find out what sound is, how it is made, and why we may call the voice a musical instrument.
The sensation which we call sound is the result of vibrations impinging on our eardrums, caused by air waves that progress rapidly outward from the initial vibrating medium, in much the same way that ripples circle outward from the spots where one skips a stone across the surface of a pond. If you can procure a tuning fork, you may demonstrate in a very simple and clear way how sound is made. By striking the fork, you may see the tines shake or vibrate rapidly back and forth, thus disturbing the surrounding air. The air vibrations, spreading out in all directions, impinge on your eardrums, one after the other, and thus excite the organ of hearing. Another simple illustration is to pluck a rubber band stretched from one place to another. In both cases you have acted as a stimulator by putting the sounding body or vibrator into motion which in turn has caused the air to vibrate at the same rate. The ear, however, does not detect all sounds caused by vibrating bodies, for many of them are too weak and indistinct. It is therefore necessary, in addition to the factors previously mentioned, that the vibrating waves have sufficient power to reach the car. Strength of sound is due to the force with which it is generated and to reinforcement which is furnished by certain surrounding bodies called resonators.
In a musical instrument, such, for example, as the violin, the movement of the bow across the strings sets the latter in vibration. The moving how is the motor or stimulator and the strings are the vibrator. The resulting sound, however, would be weak and lacking its characteristic quality if it were not for the violin box with its volume of air, which, acting as a sympathetic resonator, reinforces the sound generated by the strings. In the clarinet the tone is made by a reed fluttering back and forth between the air cavity in the mouth of the player and the air cavity in the instrument. In this case the player is the motor, the reed the vibrator, and the tube of the instrument with its column of air the resonator.
The voice, although considerably more complicated, can be illustrated in like manner. The larynx, or voice box, located in the throat, has two elastic membranes stretched across it, which are commonly known s vocal cords. This term, however, is somewhat misleading, for it gives the impression that they are strings similar to those on the violin. As a matter of fact, they are more like the edges of lips or delicate bands. When the breath stream (the motor or stimulator) passes through the larynx, the vocal cords (the vibrator) may come together at the will of the player and be made to vibrate. The sound produced is reinforced or strengthened by the cavities of the throat, nose, and mouth which form the chief resonators of the vocal instrument.
Although the voice has been compared to other musical instruments, it has some features which make it distinctive. In addition to the motor, vibrator, and resonators common to all instruments, it possesses an articulator formed by the tongue, lips, palate, jaws, and teeth which make possible the formation of words. Also, unlike the resonating chambers of other musical instruments, certain parts of the resonators of the human mechanism can be changed at will through movements of tongue, teeth, lips, jaw, and palate. Hence, a great variety of sounds is possible.