WEDNESDAY afternoon in Fairfield Working Men's Club in Govan, and the joint is jumping like a flea on a trampoline.

The usual tea-dance crowd have been joined by faux beatniks, contemporary rockabillies and other student types. It's like Top of the Pops seen through a flu dream. Suddenly, a medical emergency is declared. "I've got a blister!"

Welcome to the nicely weird world of God Help the Girl, the first feature film directed by Stuart Murdoch, better known as the frontman of Glasgow indie band Belle and Sebastian. It's a musical, as you might have guessed, with the injury sustained by one of the young dancers, and it has been a long time coming.

Murdoch first had the idea in 2003. He thought the screenplay would take a year to write. Nine years have now passed, with Belle and Sebastian tours completed and albums released (including one for God Help the Girl). All the while, the bands' songs featured in movies including 500 Days of Summer, Juno, and The Devil Wears Prada. But still there was no sign of Murdoch shouting "action" on his own movie.

A visit to the set shows how that has changed. Murdoch, with the aid of his producer, Barry Mendel, is finally in the thick of it. With the producer of Rushmore, The Royal Tenenbaums and Munich on board, the film is now on schedule to meet its 2013 release date.

Murdoch, 43, thought the shoot was going to be the hardest part and was worried about his stamina (he had chronic fatigue syndrome in his twenties). "I'm a guy in a band, we don't work very hard. These guys work crazy hours." He had also been concerned about having all the answers to the many questions that come a director's way. He's been pleasantly surprised though. "This is the fun part."

The budget (put by Mendel at between £1 million and £2m) has been raised from Creative Scotland, plus the usual tax-break given to UK films. The rest comes from "crowd sourcing" whereby individuals, in this case mostly Belle and Sebastian fans, pledge money in return for anything from a thank you postcard from Murdoch to a listing in the end credits.

Murdoch isn't worried about so many people having a stake in the movie. If anything, he says, he has more freedom than if a big studio was backing the film. "There is no studio. We're the studio ... I'm very lucky, a first-time director who gets to do pretty much what he wants – very rare."

God Help the Girl is all about Eve (played by Emily Browning), a young woman who travels to Glasgow for university, ends up adrift, and finds her way back through writing songs. Though there are "bits and pieces" from his own life in the story, Murdoch says it's not purely autobiographical.

The film is set in Glasgow, Murdoch's adopted home city (he's from Ayr originally). Mendel is enjoying filming here, finding it makes a change from the blockbuster experience. "This crew is very light on its feet, we move very quickly. I like that, there's a lot more energy in the shooting day."

There's the odd unexpected treat, too. One scene called for what Mendel calls a couple of "questionable characters", but the actors cast looked rather too sweet for Murdoch's taste. Cue directorial despair until a couple of locals wandered along. Within five minutes they were in the scene, dancing like professionals. "Everybody said 'did that really happen?'" laughs Mendel.

Mendel has been on the same page as Murdoch since contacting the band's office a few years ago to say if they ever wanted to get involved in film to give him a call. Murdoch did, going out to Los Angeles to work on a screenplay.

"Barry would give me copious notes about where I was going wrong with the script. I learned an awful lot. I never expected I'd be sitting in a cheap motel room in Los Angeles trying to work up my screenplay."

Mendel chips in: "Like F Scott Fitzgerald."

Murdoch hasn't been fazed at the multitasking involved in directing a cast and crew, comparing it to being in the multimember Belle and Sebastian. He likens his director of photography to band member Stevie Jackson, the first assistant director ("he's the guy that runs around and shouts a lot") to Bob Kildea, with Mendel as Richard Colburn on drums. Some of the band appear in the film (Sarah Martin plays a nurse), or are helping with the music.

Mendel, a long-time fan of the band, is looking forward to hearing Murdoch's songs being brought to life by the man himself.

"When music is used well, like in a Spike Lee movie or a Scorsese or Tarantino, it helps illuminate a whole new side of the song, it gives the song even more life and vibrance. That takes a special filmmaker and a special kind of marriage."

He turns to Murdoch. "I don't think that's happened with your songs, ever."

Murdoch shakes his head. "Never, I'm afraid to report. I would trade them all for one Mrs Robinson moment, one song the whole scene has been based around."

Now he has his chance. Once the film comes out, will that be the end of Belle and Sebastian? No, says Murdoch, the band has always had its side projects, breaking away and coming back again. "We'll be back for next summer," he promises.