University of Edinburgh
Abstract :
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.