The influence of pipe organ reed curvature on tone quality

Although organ flue pipes have been widely studied, the same claim cannot be made for pipe organ reed stops. Given certain design constraints, such as the type of reed stop being voiced and the desired tone quality, the reed voicer must use consummate skill to curve the reed tongue so as to produce the best and most stable tone as well as to guarantee that each pipe blends with its neighbors. The amount and type of curve given to a reed tongue influences not only the harmonic structure of the steady-state sound but also the attack. There are two fundamentally different types of curvature that can be given to a reed tongue, the trompette (chorus reed) curve (which gives a bright sound) and the smooth-toned curve employed for clarinet pipes. This study investigated the effect of reed curvature on the vibration and tone (as assessed by professionals) on reed tongues of both types. Two F2 (8'F, 87.3 Hz) pipes (a trompette and a clarinet) were constructed and voiced with differently curved tongues to produce a variety of tones. The vibration of the reed tongue was measured under typical conditions by laser vibrometer; the pressure waves in the boot and in the shallot were measured by means of one-quarter inch microphones, and the pipe's sound was recorded at the egress. By performing various measurements simultaneously, phase differences were also determined, the extreme sensitivity of tone to reed curvature was demonstrated, and a recently proposed theory of reed vibration was shown to be more accurate than the standard model.