Kathleen Schlesinger

“ FREE REED VIBRATOR (Fr. anche libre, Ger. durchschlagende Zunge, Ital. ancia or lingua libera) , in musical instruments, a thin metal tongue fixed at one end and vibrating freely either in surrounding space, as in the accordion and concertina, or enclosed in a pipe or channel, as in certain reed stops of the organ or in the harmonium. The enclosed reed, in its typical and theoretical form, is fixed over an aperture of the same shape but just large enough to allow it to swing freely backwards and forwards, alternately opening and closing the aperture, when driven by a current of compressed air. ”

“ The most valuable characteristic of the free reed is its power of producing all the delicate gradations of tone between forte and piano by virtue of a law of acoustics governing the vibration of free reeds, whereby increased pressure of wind produces a proportional increase in the volume of tone. The pitch of any sound depends upon the frequency of the sound-waves, that is, the number per second which reach the ear ”

“ The power of the overtones and their relation to the fundamental note depend greatly upon the form of the tongue, its position and the amount of the clearance left as it swings through the aperture.
Free reeds not associated with resonating media as in the concertina are peculiarly rich in harmonics, but as the higher harmonics lie very close together, disagreeable dissonances and a harsh tone result. The resonating pipe or chamber when suitably accommodated to the reed greatly modifies the tone by reinforcing the harmonics proper to itself, the others sinking into comparative insignificance. ”