Jamaican music can be roughly divided into four eras, each with a distinctive beat - ska, rocksteady, reggae and dancehall. Ska dates from about 1960 to mid-1966, rocksteady from 1966 to 1968, while from 1969 to 1983 reggae was the popular beat. The reggae era had two phases, "early reggae" up to 1974 and "roots reggae" up to 1983. Since 1983 dancehall has been the prevalent sound. The authors describe each stage in the development of the music, identifying the most popular songs and artists, highlighting the significant social, political and economic issues as they affected the musical scene. While they write from a Jamaican perspective, the intended audience is "any person, local or foreign, interested in an intelligent discussion of reggae music and Jamaica.".