DJ Screw, a.k.a. Robert Earl Davis Jr., changed rap and hip-hop forever. In the 1990s, in a spare room of his Houston home, he developed a revolutionary mixing technique known as chopped and screwed. Spinning two copies of a record, Screw would "chop" in new rhythms, bring in local rappers to freestyle over the tracks, and slow the recording down on tape. Soon Houstonians were lining up to buy his cassettes--he could sell thousands in a single day...