Style triumphs over substance in Doug Pray’s agile, intelligent documentary, which investigates the phenomenon of the DJs who contribute to hip-hop music the rhythmic riffs produced by the movement of stylus against vinyl LPs on old-fashioned phonograph turntables. The piece simultaneously promotes the notion that turntablism, as it’s called, is the equivalent of playing a musical instrument, offers a general history of the practice, and introduces those who’ve been influential in advancing the “art.” “Scratch” is sufficiently well-done that you needn’t like the music to find it deftly made and intriguing. Some of the DJs featured in interviews are unusually articulate and likable; the excerpts from their performances (often in competition) are smartly edited; the depiction of their obsessive effort to find new material by culling through piles of discarded LPs and items in used record stores is revealing; and a few of the “expert commentators” are quite amusing. (A favorite is an oddball record producer who goes by the name of Naut Humon.)

On the other hand, one might wish for a more tongue-in-cheek approach to the whole business, along with a more coherent exploration of its sociological significance. “Scratch” isn’t quite as adulatory toward its subject as “Dogtown and Z-Boys” (about early “extreme” skate-boarders) is, and what it’s dealing with isn’t nearly as socially problematical anyway, but a bit more background on the DJs and a somewhat more lighthearted assessment of their contributions would be welcome. After all, at best “turntablists” add little more to music than an additional percussive element–one that’s easy to hear (like a drum) but roughly the equivalent of a condiment to a real meal.

Still, though it’s more conventional than it need have been, “Scratch” is tightly constructed, inoffensive, and–blissfully–not too loud. It’s a nifty portrait of a minor, but intriguing, element of popular culture.