Rap music originated as a cross-cultural product. Most of its important early practitioners—including Kool Herc, D.J. Hollywood, and Afrika Bambaata—were either first- or second-generation Americans of Caribbean ancestry. Herc and Hollywood are both credited with introducing the Jamaican style of cutting and mixing into the musical culture of the South Bronx. By most accounts Herc was the first DJ to buy two copies of the same record for just a 15-second break (rhythmic instrumental segment) in the middle. By mixing back and forth between the two copies he was able to double, triple, or indefinitely extend the break. In so doing, Herc effectively deconstructed and reconstructed so-called found sound, using the turntable as a musical instrument.
In the early 1970s a musical genre was born in the crime-ridden neighborhoods of the South Bronx. Gifted teenagers with plenty of imagination but little cash began to forge a new style from spare parts. Hip-hop, as it was then known, was a product of pure streetwise ingenuity; extracting rhythms and melodies from existing records and mixing them up with searing poetry chronicling life in the 'hood, hip-hop spilled out of the ghetto.
Spoonie Gee, Sylvia Robinson, George Clinton, Peter Brown, Afrika Bambaata
Kool DJ Herc, the godfather of hip-hop, was a Jamaican-born DJ who moved to the Bronx in 1967. With his unique playlist of R&B, soul, funk, and obscure disco, Herc quickly became the catalyst of the hip-hop way of life. The kids from the Bronx and Harlem loved his ghetto style, which gave birth to the concept of the B-Boy. The B-Boy -- or beat boy, break boy, Bronx boy -- loved the breaks of Kool Herc, and as a result soon created break dancing. These were the people of the hip-hop culture. While Pete DJ Jones was #1 for the black disco crowd in NYC, Herc and the B-Boys were the essence of the hip-hop movement, because of they lived the lifestyle. The way they danced, dressed, walked, and talked was unique, as opposed to most of the disco artists and fans of the time, who were not as in touch with the urban streets of America.
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Modern day rap music finds its immediate roots in the toasting and dub talk over elements of reggae music. In the early 70's, a Jamaican dj known as Kool Herc moved from Kingston to NY's West Bronx. Here, he attempted to incorporate his Jamaican style of dj which involved reciting improvised rhymes over the dub versions of his reggae records. Unfortunately, New Yorkers weren't into reggae at the time. Thus Kool Herc adapted his style by chanting over the instrumental or percussion sections of the day's popular songs. Because these breaks were relatively short, he learned to extend them indefinitely by using an audio mixer and two identical records in which he continuously replaced the desired segment.
In those early days, young party goers initially recited popular phrases and used the slang of the day. For example, it was fashionable for dj to acknowledge people who were in attendance at a party. These early raps featured someone such as Herc shouting over the instrumental break; 'Yo this is Kool Herc in the joint-ski saying my mellow-ski Marky D is in the house'. This would usually evoke a response from the crowd, who began to call out their own names and slogans.
As this phenomenon evolved, the party shouts became more elaborate as dj in an effort to be different, began to incorporate little rhymes-'Davey D is in the house/An he'll turn it out without a doubt.' It wasn't long before people began drawing upon outdated dozens and school yard rhymes. Many would add a little twist and customize these rhymes to make them suitable for the party environment. At that time rap was not yet known as 'rap' but called 'emceeing'. With regards to Kool Herc, as he progressed, he eventually turned his attention to the complexities of djaying and let two friends Coke La Rock and Clark Kent (not Dana Dane's dj) handle the microphone duties. This was rap music first emcee team. They became known as Kool Herc and the Herculoids.
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http://www.oocities.org/matthew_robison/hiphop.htm
Rap is where you first heard it [sampling] --Grandmaster Flash's 1981 "Wheels of Steel," which scratched together Queen, Blondie, the Sugarhill Gang, the Furious Five, Sequence, and Spoonie Gee --but what is sampling if not digitized scratching? If rap is more an American phenomenon, techno is where it all comes together in Europe as producers and musicians engage in a dialogue of dazzling speed.