A free-reed hand-held instrument similar to the accordion and harmonica. It is about 12 inches long with a musical keyboard on top and is played by blowing air through a mouthpiece at one end or alternatively can be played flat using a tube that fits into a hole in the side of the instrument. Pressing a key opens a hole, allowing air to flow through a reed. The keyboard is usually two or three octaves long.

The name melodica was trademarked by Hohner, who still manufacture the instrument. The alternative name, pianica, was adopted by Yamaha. Another alternative name, melodion, is used by Suzuki.