Groove Music: The Art and Culture of the Hip-Hop DJIt's all about the scratch in Groove Music, award winning music historian Mark Katz's groundbreaking book about the figure that defined hip hop: the DJ. Today hip hop is a global phenomenon, and the sight and sound of DJs mixing and scratching is familiar in every corner of the world. But hip hop was born in the streets of New York in the 1970s when a handful of teenagers started experimenting with spinning vinyl records on turntables in new ways.