Sanity feels like a distant place when you are watching the 1974 Texas Chainsaw Massacre - unless gutting folk with a power tool is your average day. That remote feeling is helped by the film's sound: initially, the only music we hear is carefree songs on the campervan radio. The noise is thin and tinny, a signal broadcast from elsewhere - elsewhere being a much safer place.

In playing their own music live to a screening of Texas Chainsaw, American country-punk duo Puerto Muerto were clearly aware of this detail, and of how the film's sounds - chickens, drillings, meat cooking - are important. So aware, in fact, that their "lost" soundtrack to the movie (from the CD Songs of Muerto County) involved 15 minutes of playing in the whole evening - if that.

Puerto Muerto's restraint probably disappointed anyone hoping for a gig's worth, but it made the bigger picture work well. They chose their moments carefully. Sally is chased by Leatherface to some country rock, with lyrics nonchalantly wondering: "What have I done?" Classic horror scenes of people opening doors they shouldn't are given a wistful twang, like moments being reminisced about rather than happening in front of us. The most insane moment of the film - dinner with the gibbering cannibals - lilts along to Puerto Muerto's Christa Meyer singing: "I cooked you your favourite dishes, and did up my hair the way you like it."

The duo's music is bleak, in a windswept way (kind of Paris Texas Chainsaw Massacre). But compared to the original soundtrack, it's a lullaby; it sounds sane. And sane - when you're watching three men helping the corpse of their granddad bash a woman over the head so she can be made into sausages - is not a word that springs to mind.