A competent, fairly comprehensive history of scratching records, this works through the history and methodology of what's now - judging by equipment sales - a more popular musical pastime than playing guitar. The film's a bit muffled when it comes to explaining the insider slang (beat-boxing?); nor is it particularly strong visually, being heavily dominated by talking heads and stuttering turntables, although the editing is often razor-sharp. Rather, the film's strength is in its cast of characters: everyone from Afrika Bambaataa and Grand Master Flash, DJs Shadow, Krush, Jazzy Jay and Shortee to the Invisibl Skratch Piklz pop up to disseminate their ideas, experience and techniques (cue home demos a go-go). Grand Master DST - of Herbie Hancock's 'Rocket' fame - and DJ Q-Bert win most of the acclaim for influence past and present; both Q-Bert and Mix Master Mike, it transpires, talk to aliens.