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44 HOPI SONGS
of inscription, the note should become entirely constant. Nor is the fact that the sharping several times disappeared in Cylinder E (inscription rate 184, reproduction rate about 175) irreconcilable with the hypothesis; for with an increased momentum the mechanism may be supposed to grow less sensitive to the delicate changes in conditions of friction involved in the movement of the needles.
As to the hurrying and slowing of the beats within the ten second spaces, it does not seem improbable that these changes may have been mainly due to very small variations in the harmonium note which was the basis of the test, reflecting the intermittent character of the supply of air from the bellows of the instrument.
As the result of this inquiry by the method of beats into the distortion of an interval sequence in phonographic reproduction, we reach the following conclusions. With a storage battery of the kind now commonly used with the instrument, which has (a) not been too long used nor too long idle; in the reproduction (b) at from 150 to 180 revolutions per minute of (c) a fresh inscription made (d) within the same limits of speed, the phonographic distortion of interval,will in general, as the component tones are taken farther apart in the inscribed sequence, gradually increase from an inappreciable amount to about 5c, or the fortieth part of a tone, this aberration taking the form of a sharping or heightening of the later tone. Further, in immediately successive reproductions of an inscribed music, corresponding tones will be apt to be given at least four or five times to within a smaller interval still, often the hundredth part of a tone or less; the total range through which the performances shift in pitch meanwhile not exceeding in general the twenty-fifth part of a tone.
As a cylinder is more used, the aberration, within individual
performances ceases to be progressive without increasing in amount, this truly wonderful fidelity of reproduction continuing as long as the inscription is audible at all.
At rates either in inscription or reproduction beyond these limits the aberration will be greater, increasing as they are farther transcended. The aberration will also in general be greater, and sometimes markedly