in music, a steam-whistle organ with a loud, shrill sound audible miles away; it is used to attract attention for circuses and fairs. It was invented in the United States about 1850 by A.S. Denny and patented in 1855 by Joshua C. Stoddard.

The calliope consists of a boiler that forces steam through a set of whistle pipes. Either a keyboard or a pinned cylinder (like that of a barrel organ or music box) controls the entry of steam into the proper pipes.