The artist formerly known as Black Francis answers the phone and explains that he can't talk; he is in crisis. I have been chasing Thompson for several days now, eager to gauge his reaction to "loudQUIETloud", a rambunctious little documentary about the Pixies's 2004 reunion tour, which debuts today at the Edinburgh International Film Festival. Directed by Steven Cantor and Matthew Galkin, the film is a bit like a Pixies song itself. It is film where simmering tensions erupt into primal storms, where high tragedy goes cheek-by-jowl with low comedy, and where the drummer goes mad and won't finish his solo. When the Pixies reformed, they invited a film crew to join them for the ride. Frank Black talks to Xan Brooks about the train-wreck of a tour that followed.