[6] Voices which by this overstrained and unnatural way of singing have become worn-out and useless may by correct, proper treatment recover, even at an advanced age, their former grace and power; and even those chronic inflammations of the larynx which are so difficult of treatment may be cured by a natural and moderate exercise of the voice in singing.
III
PHYSICAL VIEW
FORMATION OF SOUNDS BY THE VOCAL ORGAN
For the artistic culture of the singing voice the knowledge of the physiological processes during the formation of tones does not suffice. This knowledge brings us acquainted only with the instrument, the artistic treatment of which is to be learned. Having, therefore, in the preceding pages stated the most important points in the formation of tones, physiologically considered, we are now to consider more nearly the physical laws relating to the same, especially as the physical view of the subject, through the latest investigations and discoveries of Prof. Helmholtz, in Heidelberg, has so much importance for music in general. In order, however, to present a clear view of this branch of our subject, in so far as the recent advances of science can be practically applied to the improvement of the art of singing, we must recur to those natural laws which are doubtless well known to most of our readers.
In order to bring the external world to our consciousness, we are provided with various organs of sense; and as the eye is sensible to the light, the ear is sensible to sound, which comes to our consciousness either as noise (Geräusch) or as tone (Klang). The whistling of the wind, the plashing of water, the rattling of a wagon are noises, but musical instruments give us tones. When, however, many untuned instruments sound together, or when all the keys within an octave are struck on the same time, then it is a noise that we hear. Tones are therefore more simple and regular than noises. The ear perceives both by means of the agitation of the air that surrounds us. In the case of noise the agitation of the air is an irregularly changing motion. In musical sounds, on the other hand, there is a movement of the air in a continuously regular manner, which must be caused by a similar movement in the body which gives the sound. These so-called periodical movements of the sound in the body, rising, falling and repeated at equal intervals, are called vibrations. The length of the interval elapsing between one movement and the next succeeding repetition of the same movement is called the duration of vibration (Schwingungsdauer), or period of motion.
TONE, AND ITS LAWS OF VIBRATION
A tone is produced by a periodical motion of the sounding body—a noise by motions not periodical. We can see and feel the sounding vibrations of stationary bodies. The eye can perceive the vibrations of a string, and a person playing on a clarionet, oboe, or any similar instrument, feels the vibration of the reed of the mouthpiece. How the movements of the air, agitated by the vibrations of the stationary body, are felt by the ear as tone (Klang), Helmholtz illustrates by the motion of waves of water in the following way: Imagine a stone thrown into perfectly smooth water. Around the point of the surface struck by the stone there is instantly formed a little ring, which, moving outwards equally in all directions, spreads to an ever-enlarging circle. Corresponding to this ring, sound goes out in the air from an agitated point, and enlarges in all directions as far as the limits of the atmosphere permit. What goes on in the air is essentially the same that takes place on the surface of the water; the chief difference only is that sound spreads out in the spacious sea of air like a sphere, while the waves on the surface of the water can extend only like a circle. At the surface the mass of the water is free to rise upward, where it is compressed and forms billows, or crests. In the interior of the aerial ocean the air must be condensed, because it cannot rise. For, “in fact, the condensation of the sound-wave corresponds to the crest, while the rarefaction of the sound-wave corresponds to the sinus of the water-wave.”[ 7 ]
The water-waves press continually onwards into the distance, but the particles of the water move to and fro periodically within narrow limits. One may easily see these two movements by observing a small piece of wood floating on water; the wood moves just as the particles of water in contact with it move. It is not carried along with the rings of the wave, but is tossed up and down, and at last remains in the same place where it was at the first. In a similar way, as the particles of water around the wood are moved by the ring only in passing, so the waves of sound spread onwards through new strata of air, while the particles of air, tossed to and fro by these waves as they pass, are never really moved by them from their first place. A drop falling upon the surface of the water creates in it only a single agitation; but when a regular series of drops falls upon it, every drop produces a ring on the water. Every ring passes over the surface just like its predecessor, and is followed by other rings in the same way. In this way there is produced on the water a regular series of rings ever expanding. As many drops as fall into the water in a second, so many waves will in a second strike a floating piece of wood, which will be just so many times tossed up and down, and thus have a periodical motion, the period of which corresponds with the interval at which the drops fall. In like manner a sounding body, periodically moved, produces a similar periodic movement, first of the air, and then of the drum in the ear; the duration of the vibrations constituting the movement must be the same in the ear as in the sounding body.
THE PROPERTIES OF TONE (KLANG)
The sounds produced by such periodic agitations of the air have three peculiar properties: 1. Strength, 2. Pitch, 3. Timbre.