Diatonic button accordion

A diatonic button accordion or melodeon is a free reed aerophone instrument similar to an accordion. 

Similar to many other newer instruments, it was a fusion of inventions in the early 19th century.

It resembles an accordion, but it is smaller and more compact.

The main buttons are placed on the right hand, and the bass buttons on the left hand.

It produces music by pushing or pulling the bellows, which causes sound to occur. 

See also: 

Accordion, a similar instrument

Concertina, same reason as accordion

Melodica, another keyboard free reed instrument

Harmonica, free reed aerophone