Calypso (music), form of folk music developed in Trinidad, West Indies, and originally sung at carnivals. Frequently improvised, the words of calypso songs usually concern topical or satirical themes, and they are characterized technically by arbitrary shifts in the accentuation of everyday English words. In Trinidad, calypso music is generally sung to a guitar and maraca accompaniment that establishes a complex counterrhythm with the voice of the singer in a style probably based on the percussive rhythms of native African music. Since about 1945, steel drums (oil drums, modified and tuned) have also been used, often played in bands.