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MECHANISM OF A 'REED: [V. § 60.
When the tongue occupies any position intermediate between that of (A) and its position of equilibrium, air is blown through the aperture in the direction indicated by the arrows in (A). From the moment that the tongue passes through its equilibrium-position towards that shown in (B), the current of air is barred by the accuracy with which the tongue fits into the aperture beneath it. Only when the tongue again emerges can the air resume its passage.
A series of equal impulses of air are thus produced at equal intervals of time and the instrument, therefore, gives rise to a regular musical sound. Its clang is highly composite containing distinctly recognisable partial-tones up to the 16th or 20th of the series. Thus a reed does not require to be associated with a resonating column in order to produce a musical sound ; in fact the instrument called the harmonium consists of reeds without such adjuncts. The timbre of an independent reed is, however, characterised by too great intensity on the part of the higher partial-tones. It is desirable to correct this defect by strengthening the fundamental-tone of the clang. This is done by placing the reed in the mouth of an open pipe whose deepest tone coincides with the fundamental-tone of the reed-clang. This tone will then be most powerfully reinforced by resonance. The other partial-tones of the clang will