Dance in the American theater normally is associated with musical comedy, although other genre may include dance. Some historians believe that musical comedy is this country's contribution to world theater, although it is not exclusively an American invention. The Black Crook, by Charles M. Barras (1866), often is considered the first musical comedy. This production was a combination of ballet, burlesque, extravaganza and melodrama. George M. Cohan was one of the first to develop an effective format for bringing comedy, dance, and music into a unified show. Musical numbers usually include several love songs, some comic songs, and chorus numbers. Popular dances of the period also are included.