So many everyday sounds come and go in i-hop, the instrumental realm of hip-hop, most of which is produced entirely in the studio with computers, turntables and found audio cues. There’s the acoustic handshake of a fax or modem, the click of a typewriter in full noir mode, the explosion of gunfire. All of them bring attendant culture associations, social context and unique sonic qualities. Infamy, a film about graffiti culture directed by Doug Pray (whose Scratch documented turntablism), features a theme song by DJ Z-Trip built around that tumble of percussives specific to the jangle of spray paint (MP3). The beat is stealthy yet bold, true to the graffiti artist’s state of mind; the occasional verbal sample appears to have been pulled from the documentary footage. And that sample of the spray can pops up occasionally, like nothing so much as a pair of dice. Since Z-Trip is best known for his pioneering “live mash-up” style, which finds unlikely parallels between various pop songs, it’s welcome opportunity to hear an original composition, this one a collaboration with Garron Chang. More on the film at infamythemovie.com and on Z-Trip at djztrip.com.