The steel band consists of several steel drums, usually made from oil drums; such bands first developed in the 1930s and 40s in the West Indies. To make a pan from an oil drum, the headis pounded into a concave shape and the position of each note is marked on the surface with a steel punch; the metal is then tempered and the drum-barrel is cut to the required length before the instrument is finally tuned. There are three basic types: tenor pans, rhythm pans, and bass pans, all of which are included in the steel band.