Accordion reeds, cavity resonance, and pitch bend.

Abstract

In keyed free reed instruments such as accordions and concertinas, the reeds are mounted over cavities that have little effect on the vibration of the reed itself, because resonances between the reed and cavity are rarely encountered. In fact, in conventional instruments, resonances can interfere with the self-excitation mechanism of the reed and become problematic to the builder. On the other hand, one can exploit such resonances in order to produce pitch bend and other acoustic effects, by intentionally designing the cavity for near resonance and by providing a mechanism that permits the musician to engage resonance at will. First, conventionally designed cavity resonance is investigated over the frequency range of the instrument, illustrating the thoroughness and facility with which cavity resonance can be designed out of conventional instruments. Finally, cavity designs and linkage mechanisms to exploit desirable acoustic effects of cavity resonance are illustrated.