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Rap:

To the untrained ear, all rap and hip-hop may sound the same, but there's a number of different levels in even the simplest rap song. 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.

Hip hop:

In the terminology of rap music, Hip-Hop usually refers to the culture — graffiti-spraying, breakdancing, and turntablism in addition to rapping itself — surrounding the music. As a style however, hip-hop refers to music created with those values in mind. Once rap had been around long enough to actually have a history, hip-hop groups began looking back to old-school figures including MCs like Kurtis Blow and Whodini, and DJs like Grandmaster Flash and Afrika Bambaataa. In fact, the latter's Zulu Nation collective sprang up in the late '80s around two of the most notable hip-hop artists, De La Soul and A Tribe Called Quest. With rap music's mainstream breakout during the '90s, dozens of hip-hop artists pointed the way back to the old school, including underground rappers like Mos Def and Pharoahe Monch.

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