Public Enemy rewrote the rules of hip-hop, becoming the most influential and controversial rap group of the late '80s and, for many, the definitive rap group of all time. Building from Run-D.M.C.'s street-oriented beats and Boogie Down Productions' proto-gangsta rhyming, Public Enemy pioneered a variation of hardcore rap that was musically and politically revolutionary. With his powerful, authoritative baritone, lead rapper Chuck D rhymed about all kinds of social problems, particularly those plaguing the black community, often condoning revolutionary tactics and social activism. In the process, he directed hip-hop toward an explicitly self-aware, pro-black consciousness that became the culture's signature throughout the next decade.