A music box is a mechanical assembly with such things as clockwork, rotating cylinders, pins, and steel combs, arranged in a way that causes music to be played once the device is wound up. The tune that is played is encoded in the arrangment of pins. Music boxes developed out of the snuff boxes of the 18th century, and were popular in the 19th century but declined in popularity once other musical devices from player pianos to phonographs were invented. They still exist as a novelty device.
A song called "Music Box Dancer", with a style resembling a music box (though real instruments were used, not an actual music box) was a hit for Frank Mills in 1979, after it was mistakenly sent to a pop radio station (it had been intended for the easy-listening market) and was played there and proved popular.