A capella group music. Began in the cities of the United States in the 40's, much as hip-hop did in the 70's - kids lacking money for instruments used what they had handy. The name came from the onomatopoetic way the voices replicated instrument sounds. Every neighborhood had a group or three, much as many neighborhoods today have DJs and MCs. Roots: gospel music and the migration of blacks to the north. Branches: vocal groups of the rock and roll and soul music eras.