Steel Drums are tuned gong made from the unstoppered end and part of the wall of a metal shipping drum. The end surface is hammered concave, and several areas are outlined by acoustically important chiseled grooves. It is heated and tempered, and bosses, or domes, are hammered into the outlined areas. The depth, curvature, and size of each boss determine its pitch. The drums are struck with rubber-tipped hammers.
Steel drums originated in Trinidad, in the West Indies, in the 20th century and are played in ensembles, or steel bands, of about 4 to 100 performers. Drums are commonly made in four sizes from bass to treble, called boom, cellopan, guitar pan, and ping pong.