Abstract: Improved performance and versatility of a free-reed instrument by linking a key of the instrument to a variable geometry chamber, which provides modifications in musical tones. The instrument can be an accordion or other free-reed instrument, and a passageway of the chamber is manipulated to alter the combined pitch and timbre of the tones.

Abstract: A register switching device in which each key of the proposed device is finger-pressed and carrier a pusher and a pivoted lever. The register switching keys are mounted on a common axle with each key adapted to be set in two positions. In one position, the pusher interacts with a moderator plate shifting lever. In the other position, the pivoted lever is arranged close to the moderator plate shifting lever and enters into engagement with a plate movably arranged along the key axle. As the plate is shifted by an auxiliary chin key, it brings the pivoted lever into engagement with the moderator plate shifting lever, thereby causing register switching.