Turntablists are DJs who use vinyl disc records, and turntable techniques like scratching or beat juggling in the composition of original musical works. Turntablism is generally focused more on turntable technique and less on mixing, rapping or vocal delivery.
Turntablists like Rob Swift, Q-Bert, A-Trak, and Kid Koala owe a certain debt to old school DJs like Grand Wizard Theodore, Grandmaster Flash, Afrika Bambaataa, and DJ Kool Herc who originally developed many of the concepts and techniques that evolved into modern turntablism. There are also more experimental turntablists such as Christian Marclay, Otomo Yoshihide, Philip Jeck and Janek Schaefer.
Turntables were actually first used as musical instruments in the 1940's and 1950's by musique concrete and other experimental composers, such as John Cage, who used them in a manner similar to digital sampling. Hip hop dj's developed independently of the earlier techniques.