At its core, hip-hop is a post-modern musical genre that deconstructs familiar sounds and songs, rebuilding them as entirely new, unpredictable songs. Early rap records, commonly called "old school," were made by DJs scratching records and playing drum loops, with MCs rapping over the resulting rhythms. As the genre progressed, hard-rock guitars and hard-hitting beats were introduced by Run-D.M.C., the first hardcore rap group, and the scratching techniques were replaced by sampling. With their dense collages of samples, beats and white noise, Public Enemy took sampling to the extreme, and they helped introduce a social and political conscience to hip-hop. That faded in the '90s, as gangsta rap — originally introduced by NWA, who used Public Enemy's sound as a template — became the dominant form. By the '90s, gangsta rap, which originally was in direct opposition to such pop-oriented rappers as MC Hammer, had become smoothed over and stylish, and consequently was more popular than ever, as evidenced by the success of pop-gangsta Puff Daddy.

Reggae
Reggae is a music unique to Jamiaca, but it ironically has its roots in New Orleans R&B. Reggae's direct forefather is ska, an uptempo, rhythmic variation based on the New Orleans R&B Jamaican musicians heard broadcast from the US on their transistor radios. Relying on skittering guitar and syncopated rhythms, ska was their interpretation of R&B and it was quite popular in the early '60s. However, during one very hot summer, it was too hot to either play or dance to ska, so the beat was slowed down and reggae was born. Since then, reggae has proven to be as versatile as the blues, as it lends itself to a number of interpretations, from the melodic rock steady of Alton Ellis and the rock and folk-influenced songwriting of Bob Marley to the trippy, near-psychedelic soundscapes of dub artists like Lee "Scratch" Perry. It has crossed into the mainstream through the bright, bouncy "reggae sunsplash" festivals and pop-oriented bands like UB40, but more adventurous reggae artists, such as Marley and Perry, have influenced countless reggae, folk, rock and dance artists. Their contributions resonate throughout popular music.

New Age
Born from an aesthetic that aims to induce a sense of inner calm, new age music emerged from the meditational and holistic fields. Generally, these are harmonious and nonthreatening albums that are allied with new age philosophies encouraging spiritual transcendence and physical healing. Some of these albums are artistically satisfying as well as therapeutic.