In addition to the popular jazz and swing music listened to by mainstream America, there were a number of other genres that were popular among certain groups of people—e.g., minorities or rural audiences. Beginning in the 1920s and accelerating greatly in the 1940s, the blues began rapidly diversifying into a broad spectrum of new styles. These included an uptempo, energetic style called rhythm and blues (R&B), a merger of blues and Anglo-Celtic song called country music and the fusion of hymns and spirituals with blues structures called gospel music. Later than these other styles, in the 1940s, a blues, R&B and country fusion eventually called rock and roll developed, eventually coming to dominate American popular music by the beginning of the 1960s.