While the term can refer to several different musical sensibilities, Hardcore Rap is marked by confrontation and aggression, whether in the lyrical subject matter, the hard, driving beats, the noisy sampling and production, or any combination thereof. Hardcore rap is tough, streetwise, intense, and often menacing (although the latter isn't always the case; there is room for humor and exuberance as well). Gangsta rap is the style most commonly associated with hardcore rap, but not all hardcore rap revolves around gangsta themes, even though there is a great deal of overlap, especially among hardcore rappers of the '90s. The first hardcore rap came from the East Coast during the late '80s, when artists began to move away from party rhymes and bragging about their microphone skills; their music and language began to reflect the gritty, often harsh urban surroundings in which it was usually created and enjoyed. Before any specific formula for gangsta rap had been invented, artists like New York's Boogie Down Productions and L.A.'s Ice-T were committing detailed observations of street life to tape; plus, Public Enemy's chaotic sound collages were setting new standards for production power, and N.W.A. celebrated the bleakness of the ghetto and the gangsta lifestyle with an over-the-top machismo. In the early '90s, hardcore rap was essentially synonymous with West Coast gangsta rap until the 1993 emergence of the Wu-Tang Clan, whose spare, minimalistic beats and haunting string and piano samples became a widely imitated style. With its slamming, hard-hitting grooves and street-tough urban grit, hardcore rap became hip-hop's most popular crossover style during the latter half of the '90s, its subject matter now a mix of party anthems, gangsta's money/sex/violence obsessions, and occasional social commentary. Artists like the Notorious B.I.G., DMX, and Jay-Z became platinum-selling superstars, and Master P's brand of gangsta-oriented Southern hardcore also became a lucrative commercial force, even if it didn't produce crossover hit singles on the same level.