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.