IN THE MID-1970 S rap music began to develop in New York City. At the time it was an unknown type of music that existed in one small corner of a great big city. It was played by DJs who traveled to local parks and community centers, stole electric power for their equipment from city lights, and hosted parties at which they refined their techniques. Few, if any, people at these gatherings knew that rap would revolutionize popular music. No one could have guessed the controversy it would cause or the debates it would ignite.

Roughly fifteen years later, people across the United States couldn't stop talking about rap music, specifically, a Florida group named 2 Live Crew. The group's album, As Nasty as They Wanna Be, had been labeled something that no other sound recording in U.S. history had—U.S. District Court judge Jose Gonzalez...