University of Edinburgh
The generation of a pitched note on a reed instrument involves a nonlinear acoustic coupling between the mechanical reed and the air column of the instrument. Once a stable regime of oscillation has been achieved the reed vibrates at the playing frequency, which is much lower than the reed natural frequency. On windcapped instruments like the crumhorn a change in the playing frequency is initiated by opening or closing toneholes. This modifies the acoustic resonances frequencies of the air column, and the pressure feedback to the reed causes its vibration frequency to change. Factors affecting the transients during rapid pitch changes on a bass crumhorn have been investigated using high speed video recording of reed motion, laser-based position tracking of the reed tip vibration, and measurements of pressure upstream and downstream of the reed.
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