A musical instrument that produces sound by sending steam through whistles, originally locomotive whistles. It was patented by Joshua Stoddard of Massachusetts in 1855, although it is based on previously known concepts.

The calliope is also known as a steam organ or steam piano. It was often played on riverboats and in circuses, where it was sometimes mounted on a carved, painted and gilded horse-drawn wagon in a circus parade.

Stoddard's original calliope was attached to a metal roller set with pins as in a contemporary clockwork music box. The pins on the roller opened valves and blew the whistles. Later, Stoddard replaced the cylinder with a keyboard, so that the calliope could be played like an organ.

Starting in the 1900s, calliopes began using music rolls instead of a live musician. The music roll operated in a similar manner to a piano roll in a player piano, mechanically operating the keys. Many of these mechanical calliopes retained keyboards, allowing a live musician to play them if needed. During this period, compressed air began to replace steam as the vehicle of producing sound.

Most calliopes disappeared in the mid-20th century, as steam power was replaced. Without the demand for technicians that mines and railroads supplied, no support was available to keep boilers running. Only a few calliopes have survived, and these are rarely played.