ACCORDION, a small portable reed wind instrument with keyboard, one of the smallest members of the organ family, in vented in 1829 by Damian, in Vienna. It consists of a bellows of many folds, to which is attached a keyboard with from five to 5o keys. The keys on being depressed, while the bellows are being worked, open valves admitting the wind to free reeds, the pitch of the note being determined by the length and thickness of the reeds. The right hand plays the melody on the keyboard, while the left works the bellows and manipulates the two or three bass harmony keys, which sound the simple chords of the tonic and dominant. The archetype of the accordion is the cheng (q.v.) or Chinese organ, between which and the harmonium it forms a connecting link structurally. Improvements in the construction of the accordion produced the concertina (q.v.), melodion and melophone.