Rather like the documentary Afghan Star from last year, this riveting piece of drama provides a great service to western audiences: it shows us the vibrant but repressed society behind the news reports. As with the other film, the vehicle to do so, and the motivation of the protagonists, is music.

Of Iran’s 72 million people, two thirds are under 30. No wonder there is a thriving music scene. Young people come together to make indie, heavy metal, jazz and rap, all of which is banned by the Islamic state authorities. We follow, fly-on-the-wall style, Negar and Ashkan, two young musicians fresh out of jail, trying to form a band in order to put on a concert in London. At every step their efforts are thwarted – no permits, no visas, no passports – and they encounter bands playing in cellars, cowsheds and makeshift attics, forever dodging the authorities. Their main hope is Nader, a fast-talking hustler who promises to solve their problems and even manages to wangle himself out of a sentence of seventy-five lashes.

Many of the music sequences are fast cut to scenes around Tehran so we glimpse, not just the modern city – the traffic, the shopping malls and the underground, but also the squalor, poverty and drug addiction. It doesn’t really matter how much you like the music being made because what shines through is the earnest creativity of the artists involved, and their frustration at not being able to be heard. It is all depressingly reminiscent of Eastern Europe before 1989.

This is not just an excellent film, it is a brave one. Shot surreptitiously over just 17 days and necessarily a little rough around the edges, director Bahman Ghobadi was arrested twice. He and his two leads, having premiered the film at Cannes, are unlikely to go back to Iran.