N.W.A is the group most frequently associated with the founding of gangsta rap. Their lyrics were more violent, openly confrontational, and shocking than those of established rap acts, featuring incessant profanity and, controversially, use of the word "nigga". These lyrics were placed over rough, rock guitar-driven beats, contributing to the music's hard-edged feel. The first blockbuster gangsta rap album was N.W.A's "Straight Outta Compton", released in 1988. "Straight Outta Compton" would establish West Coast hip hop as a vital genre, and establish Los Angeles as a legitimate rival to hip hop's long-time capital, New York City. "Straight Outta Compton" sparked the first major controversy regarding hip hop lyrics when their song "Fuck tha Police" earned a letter from FBI Assistant Director Milt Ahlerich, strongly expressing law enforcement's resentment of the song.