Are you ready to rock? Get your horned salutes at the ready for Alexandra Lipsitz’s documentary, following the World Air Guitar Championships’ first US entrants: the face-melting sensation that is C-Diddy and the rougher-edged Bjorn Turoque. The tricksy issue of a ‘semi-pro’ Yank performer turning up to boss an amateur Euro-comp is strummed over in favour of some basic goodtime riffage. You’re never quite sure if you’re laughing at or with these guys, displaying the sort of self-delusion not seen since Neville Chamberlain left Munich. But you will be entertained even if, in rock’n’ roll terms, it’s less satanic metal than cutesy chart pop.