The accordion is a small, portable box-shaped instrument with metal reeds, which vibrate as air, distributed by a bellows, flows across them. The principle of sound production on the accordion is the same as the harmonica, the difference being that the former is equipped with a bellows and keys that produce the desired tones. Just like the piano, the accordion is a keyboard instrument with a range of 3 ½ octaves. It is designed to be held in both hands, which move towards or away from each other, compressing or expanding the bellows. The keys or buttons that produce the melody are played with the fingers of the right hand, while the buttons that produce simple chords for accompaniment are controlled by the left hand. Damian of Vienna is credited with inventing the accordion.