After nearly 30 years in business and 10 albums in, Glaswegian cacophonists Mogwai have earned the right to an adulatory documentary – and they get one here, directed by former photographer Antony Crook. It has a purist approach, taking cues from the band’s anti-logorrheic approach by offering only a loose biography and comparatively little by way of analysis. All the better to let their majestic instrumental squalls fill the space, unencumbered by too much guiding commentary. Kicking off just as Mogwai find themselves on the cusp of an unlikely UK No 1 for their last album, As the Love Continues, the film dips back to the late 90s to find them committed early on to meting out exactly the same widescreen guitarscapes. Alex Kapranos, who first put them on stage at the 13th Note Café, speculates that these emotional workouts are expressing what taciturn Glaswegian men usually don’t. Remembering getting the band to record a version of Jewish prayer Avinu Malkeinu (the 2001 single My Father My King), producer Arthur Baker inadvertently puts a finger on the religious-ecstatic nature of Mogwai live. But it’s writer Ian Rankin who identifies the band’s loud/soft dynamics as belonging to a tradition of “Scottish antisyzygy”. Stuart Braithwaite and bandmates are a curiously indirect presence, filmed in the studio and on stage but only occasionally getting caught up in authorial narration. But with the film splicing together different performances of the same song to make these compositions seem even more like gigantic, evolving, saurian entities, the music does the talking. In fact, the film is something of a muso manifesto, especially when Mary Anne Hobbs lauds them for having remained staunchly independent. With Crook offering scant details of how the approach has worked for Mogwai down the years on an economic and personal level, it’s hard to weigh the worth of that. But if current bands might not find their example viable in a changed industry, the sonic Sturm und Drang is undeniable. Mogwai: If the Stars Had a Sound is in UK and Irish cinemas on 19 November only.