No One Knows About Persian Cats, Bahman Ghobadi, 103 mins, (12A)

There's nothing velvet about this underground

Rock musicians love to strut their outlaw credentials, but there have always been places where certain types of music really will make you an outlaw. Take Iran, where performing or listening to Western music is very much frowned upon by the authorities.

No One Knows About Persian Cats is a tribute to Iran's underground music scene from Kurdish director Bahman Ghobadi, who made a splash on the art-house circuit a few years ago with A Time For Drunken Horses, an intense rural drama about smuggling across the Iran-Iraq border. A very different enterprise, but similarly about contraband activities, No One Knows About Persian Cats – visually rough-edged and filmed surreptitiously during 17 days – is part reportage, part "let's-do-the-show-right-here" fiction. Its central figures are young musicians Negar and Ashkan (Negar Shaghaghi, Ashkan Koshanejad), a woman and a man respectively, both fresh out of prison for their musical activities but undeterred, and planning to assemble a band to play a London gig.

Ghobadi follows these two sweet-natured, distinctly talented hopefuls through the Tehran underworld, from rehearsal cellar to recording studio to cowshed – anywhere instruments can be set up on the sly – as they try to recruit accomplices for their gentle but spirited indie pop. In fairness, the duo are rather less interesting than some of the talents they encounter. These include a dazzling blues chanteuse named Rana Farhan, a stocky sound engineer who doubles as a foghorn blues rasper in the Howlin' Wolf mould, the heavy- metal denizens of the aforementioned cowshed, and a rather impressive rap artist (named Hichkas, but I wonder if his homies call him 50 dirhams?) who proves that the usual hard-times-in-da-hood material works just as well, if not better, in Farsi.

There's an uneasy balance between the narrative and the music sequences, some of them shot as serviceable MTV pastiche – sunkissed postcard images for the more traditional performers, montages of bustling Tehran life for those singers who presumably preferred not to have their faces appear on screen. Some viewers might not consider it such a revelation that Tehran's music scene is populated by ardent Sigur Ros fans and slackers in Strokes T-shirts – although, admit it, you would never have guessed such things from most of the Iranian films we've seen in Britain.

The show is stolen by Hamed Behdad as Nader, an energetic but unreliable hustler who promises to take care of the young couple's affairs. A speed talker who rivals Martin Scorsese for manic velocity, Behdad has a fantastic scene – comic and terrifying in equal measure – in which he frantically tries to argue his way out of a punishment of 75 lashes for possessing Western DVDs.

This is ultimately not a happy story, as befits the subject, but it's a vivid snapshot of a hitherto under-publicised scene. And it's a welcome reminder – in our blasé download era – that in some cultures, music can still be not only hard to find but also, as the phrase goes, as serious as your life.