Rhythm and blues evolved during World War II and is a form of Black dance music. Its development is associated with economic, demographic, and social changes that occurred in American society during the 1940s and 1960s. Primarily recorded by small, regional independent record labels, the term “rhythm and blues” was first used as a marketing label to identify all types of secular music recorded by and for African Americans. From urban and rural blues, boogie-woogie, swing, jazz combos and trios, to solo dancers and vocal harmony groups, rhythm and blues encompassed all Black musical traditions. As a musical style, the term identified as a music genre that was a hybrid of elements from gospel music, blues, jazz, and later, pop.