Beach music, also known as Carolina beach music, is a regional genre which eveloped from various musical styles of the forties, fifties and sixties. These styles ranged from big band swing instrumentals to the more raucous sounds of blues/jump blues, jazz, doo-wop, boogie, rhythm and blues, reggae, rockabilly and old-time rock and roll. Beach music is closely associated with the style of swing dance known as the shag, or the Carolina shag, which is also the official state dance of both North Carolina and South Carolina. Recordings with a 4/4 "blues shuffle" rhythmic structure and moderate-to-fast tempo are the most popular music for the shag, and the vast majority of the music in this genre fits that description.