As with the pop and alternative designations, hip-hop music has continued to evolve and encompass entirely new forms. The hip-hop of the late '70s and early '80s, which included acts like the Sugar Hill Gang and Run DMC, bears almost no resemblance to modern-day outfits such as the Roots and Outkast. Still, these groups are continually slapped with the hip-hop tag, even if the styles they inhabit fall at opposite ends of the musical spectrum.

In the years between then and now, a succession of hip-hop music stars have commanded center stage and threatened to redefine yet again the conventions of an art form that critics and fans thought they understood. NWA brought the world "gangsta" rap, while Eminem helped pioneer the art of "id" rap, based largely on the notion of "freestylin." Along the way, acts like MC Hammer, Young MC, Third Bass, and the Fresh Prince left the pop imprimatur on their own peculiar musical contributions, many of which landed squarely at the top of the pop charts.

The Continuing Struggle To Define Hip-Hop Music

Anyone who's ever listened to artists like Big Daddy Kane or Eric B and Rakim could hardly confuse their sounds with those of the aforementioned "crossover" acts. Many fans of hip-hop music even take offense at comparisons between these "old skool" innovators and their rip-off artists. So where exactly does that leave hip-hop music today? Even the staunchest supporters of rap and hip-hop aren't entirely sure.

In just the past few years, hip-hop music, which was once bred with heavy metal (see Public Enemy's collaboration with the group Anthrax), has begun to meld more and more with trance and electronica. This fusion of styles should only surprise those who haven't paid particular attention to hip-hop over the past 20 years or so, for that has been the movement's defining trait. Who knows? Perhaps today's musical pioneers will continue to break new ground by cross-fertilizing hip-hop music with classical symphonic pieces by Bach or Beethoven.