Whats a tone chamber?
Also called a “cassotto,” a tone chamber is a second long wood or aluminum box inside the accordion. One or two of the reed banks are mounted inside (usually the clarinet or middle octave reeds and/or the bassoon or low reeds). The chamber takes the metallic reedy edge off the sound. Sometimes in case of the “clarinet” reeds (that often come as a pair of reed banks on larger instruments), one bank will be in the chamber and one outside so that the player has a choice. Tone chambers add to the weight and expense of an accordion.
