A portable keyboard instrument in which sound is produced by the compression of baffles, forcing air through pipes or reeds; SYN. piano accordion, squeeze box, hand organ.
Musical instrument of the free-reed organ type comprising left and right wind chests connected by flexible bellows. The right hand plays melody on a piano-style keyboard of 26 to 34 keys while the left hand has a system of push buttons for selecting single notes or chord harmonies.
Invented by Cyrill Damien (1772–1847) in Vienna 1829, the accordion spread throughout the world and can be heard in the popular music of Germany, France, China, Russia, and the US.

Arranged in parallel folds; SYN. plicate.