In the late-'70s and early-'80s, The Gap Band ruled R&B radio in the US. Their funked-up grooves helped bridge the gap between the disco era and the modern sound of R&B—while their music also became a cornerstone sample source for hip-hop artists. Check out the group's tracks fuelling one of Nas's laments on life, N.W.A.'s incendiary gangsta rap styles and The Pharcyde's introspective outings.