Scratching

Old school hip hop would often sample disco and funk tracks such as "Good Times" by Chic. However the use of funk samples went into a decline from 1983 onwards. A live band was often used, as in the case of The Sugarhill Gang. The use of extended percussion breaks led to the development of mixing and scratching techniques. Scratching was pioneered by Grand Wizard Theodore in 1977, and the technique was further developed by other prominent DJs such as Grandmaster Flash. One example includes Grandmaster Flash's "Adventures on the Wheels of Steel", which was composed entirely from Flash on the turntables. However very few tracks contained significant scratching techniques prior to 1981.

http://www.youtube.com/watch?v=3D6JooB-yVg