Accordians

Accordions come in many different configurations and types. There is no such thing as a standard accordion. Some accordions are bisonoric, which means they produce different pitches depending on if the bellows are being squeezed together or pulled apart, similar to how a harmonica will produce a different pitch depnding on if you are blowing or sucking. Others accordions are unisonoric and produce the same pitch regardless of the direction of bellows movement.