Catch-all phrase denoting black pop of various eras; applies to anything from Louis Jordan, to Johnny Otis, to Motown, to funk, to whatever crap BET is foisting upon your telly. It bears watching/listening/studying, as black music has traditionally been the Olduvai Gorge of American pop, even as it's been the sonic ghetto of yanqui apartheid.
Recommended: Charlie Gillett's
book The Sound of the City or any of Nelson George's writings on music.