On the Building up of the Tone in the “Gamba” Organ-pipe

Abstract

IN considering the nature of this pipe, and in determining the relation of its air-reed and its air-column, one fact discovered in these investigations should always be borne in mind, that the pitch of the reed is dependent not on vibrating length, but on vibrating divergence—on the amplitude of the reed's motion. The pitch of the air-column is not necessarily the same as the pitch of the air-reed; they may be and often are at variance: and this pipe will afford a happy means of demonstration of the statement made in a previous letter, that the tone of every organ-pipe is dual. As regards the reed, whatever the modifications of length by height of mouth, of thickness by varied wind-way, or of strength by amount of wind-pressure, the final result is bound by this law of divergence. In the typical air-reed, any deviation from the direct line of force taken by the stream of air is the beginning of vibration; its highest possible rate of vibration begins existence on its least divergence from the direct line; consequently, its highest pitch is its inceptive tone at this stage or condition of untamed energy. The bass has always been considered the basis and commencement of musical tone; every relation of tones has been examined on that ground, and it has undoubtedly been the source of many errors, one might almost say in the nature of superstitions, so tenacious has been its hold, so blinding its influence on the perceptions. Tone has its beginnings in the highest activity, and descends to the lowest and slowest; the development of its mechanical relations proceeds by definite degrees, and the issue depends on the affinity existing between the pipe and the reed, both possessing definite form, power, and character, and blending these by law. The vibration of the aëroplastic reed is thus shown to be isotonic, not isochronous; the laws of its vibrations are identical with those of the things most like itself, of sound-waves, of light-waves.