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Scan 30
Harvard Dictionary Of Music, 1944
16 lines. Read by computer on 18 September 2026, twice; the two readings disagreed in places. No printed page number was found. See the scan on archive.org.
1ACOUSTICS
3out producing a sound, i.e., merely raise the damper of the key of C; then strike forcefully the key of C₁ and release it at once; the higher C, corresponding to the tone of the depressed key, will clearly be heard. The experiment can be repeated by depressing the keys of G, c, e, g, etc., and striking each time the key of C₁. In every case, the tone corresponding to the depressed key will be heard. The explanation of the phenomenon is found in the fact that the harmonics C, G, c, … produced by the fundamental tone C₁ generate, by way of resonance, sympathetic vibrations in the shorter strings corresponding to these tones. The harmonics are the cause of three important musical phenomena, namely, *timbre, the *natural tones of wind instruments, and the *harmonics of the violin.
5V. Pipes. In pipes (organ pipes, and all wind instruments) an enclosed air column is caused to vibrate in what is technically termed "stationary waves." These are characterized by a regular alternation of places of highest density (nodes) and highest rarefaction (antinodes or loops) between which the density of the air decreases from the maximum to the minimum. At the place of maximum density the amplitude of the vibrating particles of air is at a minimum, and vice versa. The whole phenomenon can conveniently be described by graphs similar to that used for a vibrating string, if the point of highest amplitude is interpreted as the loop, the stationary point as the node. In an open pipe, a loop develops at each end, with a node in the middle; in a *stopped pipe, a node develops at the closed end, a loop at the open end. From the accompanying drawing it appears that an open pipe generates a sound the wave length of which is double the length of the pipe (N'N'' = [address hidden]), while a stopped pipe generates a sound the wave length of which is four times the length of the pipe (N'N'' = [address hidden]) and which, therefore, is an octave lower than that produced by an open pipe of the same length. An open pipe sounding C measures approximately eight feet [see *Foot (2)].
7Like a vibrating string, an air column vibrates not only as a whole but also in parts (1/2, 1/3, 1/4, 1/5, etc., of its length), thus producing harmonics. While an open pipe produces all the harmonics (as does a string), a stopped pipe segments so as to give out only the odd-numbered harmonics, 1, 3, 5, etc. The reason is that an even harmonic (e.g., 2) would call for a loop (or a node) at both ends of the pipe, while in a stopped pipe there is always a loop at the open end, a node at the closed end [see *Wind instruments III; *Organ IX]. one of two readings
8Like a vibrating string, an air column vibrates not only as a whole but also in parts (½, ⅓, ¼, ⅕, etc., of its length), thus producing harmonics. While an open pipe produces all the harmonics (as does a string), a stopped pipe segments so as to give out only the odd-numbered harmonics, 1, 3, 5, etc. The reason is that an even harmonic (e.g., 2) would call for a loop (or a node) at both ends of the pipe, while in a stopped pipe there is always a loop at the open end, a node at the closed end [see *Wind instruments III; *Organ IX]. one of two readings
10VI. Interference. This is the technical term (not a very fortunate one) for the numerous phenomena resulting from the superposition of two or more air vibrations. The general principles of the very complex phenomenon can be grasped from the drawing [Ex. A], showing two original vibrations (I, II) of the same frequency as well as the result of their superposition (III = I + II). More im-
12Open and Closed Pipes
14INTERFERENCE
15Ex. A: Vibrations of the Same Frequency. Ex. B: Vibrations of Different Frequencies: I, of 12 cycles; II, of 14 cycles; III, resulting vibration showing 2 (= 14 – 12) maximum vibrations per second (beats).
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