Scan 18
The New Encyclopedia Of Music And Musicians, 1929
22 lines. Read by computer on 18 September 2026. No printed page number was found. See the scan on archive.org.
1(3) No adequate statement is here practicable of the acoustical principles involved in making musical instruments. But certain fundamental points may be noted.
3Tone-producing vibrations are mostly those induced (a) in stretched strings or cords, (b) in flat tongues or reeds, fixed at one end, (c) in confined portions of air. The first is illustrated in the violin (sounded by friction), the guitar (sounded by plucking) and the piano (sounded by striking); the second by the oboe and clarinet, the reed-organ, certain stops in the pipe-organ ('the reeds'), and also, though not so obviously, by the human voice and by most of the 'brass' in an orchestra or military band; and the third by most of the stops of a pipe-organ (the 'flue-stops'). Other types are stretched membranes (as in drums of all kinds), solids of varied shape (as in bells), etc.
5(a) A stretched string, when displaced by any impulse, tends to vibrate both as a whole and in its aliquot parts, so as to yield a fundamental tone and several upper partials. The pitch varies with the string's mass, length and tension, a heavy, long or loose string giving a relatively low tone, and vice versa. A stringed instrument is said to have fixed intonation when each string yields but one tone (as in the piano), but free intonation when a single string can be made to yield more than one tone by 'stopping' (shortening its effective length) by the finger or similar agency (as in the violin, lute, harp, etc.). The quality or timbre of the tone is influenced by the nature of the string itself, the nature of the sounding-agent (whether bow, finger, plectrum or hammer), by the place on the string where the latter agency comes to bear and especially by the general structure of the instrument with reference to resonance (see below), since all these factors affect the number and balance of the upper partials. All instruments that are played with a bow have the advantage that the tone can be not only prolonged at will but varied in force and character while continued.
7(b) In reed-instruments the vibratile element is a solid strip or flap of some elastic material (wood, metal, a fold of flesh, etc.). Except in a limited way (especially in organ-pipes and the voice) pitch and quality are not so much determined by the reed itself as by the body of air contained in whatever tube or other cavity which is immediately connected with the reed and its setting. This class of instruments, therefore, merges acoustically with the next.
9The voice, as a reed-instrument, has the signal peculiarity of having a vibratile element that is highly variable as to mass, length and tension, the vocal cords being membranous folds or flaps subject to much muscular manipulation. In this case both pitch and part of quality are fixed by the reed, though quality is greatly modified by the form of adjacent cavities.
11(c) In wind-instruments like the flute and the organ (flue-stops) the vibratile element is a condensed stream of air directed against a sharp edge in such way that the stream is set into vibration (in and out as respects the edge). The pitch and quality of the resulting tone are fixed by the pipe or tube with which the sounding-orifice is connected, pitch depending on the effective length of the pipe or tube and quality on the material, shape and proportions of the latter. Wind-instruments sounded by means of a conical or cupped mouthpiece (like horns and trumpets) are properly reed-instruments, since the initial vibration occurs in the player's lip, but their acoustical action is on the whole similar to pure wind-instruments except that the tones actually used are not the fundamental of the tube, but upper partials of that tone.
13All wind-instruments, like bow-instruments, yield tones that can be prolonged and varied while continued. Most of them are actuated by the breath, though some (pipe- and reed-organs, accordions, etc.) by air artificially stored under compression.
15All important instruments make use of the principle of resonance. This is the induced or sympathetic vibration of solids and of limited bodies of air in response to tone-producing vibrations in their neighborhood. This secondary vibration blends with the primary, broadens its sonority, perhaps modifies its pitch as well as its quality, and becomes the generator of the final tones sent out to the hearer.
17In some instruments there are specific resonators for individual tones (see Marimba), but in most cases the resonator is general, adapted to seize and ennoble many different tones, singly or in combination. Thus the violin-body, with the air which it contains, serves as resonator for the entire tonal scope of the instrument. Thus the soundboard of the piano acts still more astonishingly in conjunction with the strings. Thus in the voice the cavities of the pharynx, mouth, nose and head, as well as the cavity of the chest, are adjustable resonators for the tones produced in the larynx. See Resonance, Soundboard, etc.
19Act. One of the major parts into which, for both artistic and practical reasons, a dramatic work, like an opera or operetta, is divided. Short works have but one act or at most two, while longer ones have from three to five. Each act is usually somewhat divided into scenes, but the pauses between the latter are brief and incidental, while those between acts often allow room for an intermezzo, entr'acte, act-tune, ballet or other divertissement—even (in the early days of the opera buffa) for a secondary play, intercalated with the drama proper. See Opera. G.
21Action. In keyboard-instruments, the general term for the entire mechanism whereby the muscular acts of the performer are translated into motions and adjustments within the instrument so as to cause the desired tone-production. The term is also sometimes extended to the mechanical appliances of instruments without a keyboard (like the harp, those of the wood-wind group, etc.). G.
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