The documentary, Where You’re Meant to Be, began life as a road trip with touring far-flung venues to perform his rewritten traditional folk songs in his own, unique style.
It ended up as a showdown between the indie-pop raconteur, best known for his no-holds-barred lyrics about sex, drugs and male anxiety, and one of Scotland’s greatest folk singers.
Sheila Stewart, 79 years old and regarded as folk music royalty, tore a strip off Aidan when he sang her his re-written version of a classic ballad.
She was not the only one who disapproved.
In Ness, on the Isle of Lewis, the camera unflinchingly records the audience, who either stare with malevolent disapproval at his unapologetically bawdy lyrics or chat loudly, paying no attention.
“The best bits in the film were always the sh**e gigs,” he laughs.
“That was the most uncomfortable I’ve ever felt on stage. I wasn’t scared – I just don’t see the point in singing when no-one is listening.”
Not that it bothered him. “There were loads of things that went wrong and we just said: ‘It’ll look good on the film’.”
Aidan, after all, has never been afraid of criticism.
As one half of Arab Strap, he provoked outrage – and made the national news – when he described his home town, Falkirk, as rundown, boring and violent.
“That must have been a slow news week,” he said. “It was a joke. We were just young guys – everybody slags their home town when they’re young!
“Someone threw a kebab at me – he was raging!” he recalls. “I remember thinking, what a waste of a kebab.”
Ever since those early Arab Strap years, people have told Aidan that his songs have echoes of folk music.
He became interested, particularly the centuries-old ballads that captured the life of ploughmen and farm hands.
But he wanted to make them modern and relevant.
“For years I wanted to do a tour in the traditional ceilidh style, where it actually means a gathering where everyone takes a turn,” he said.
His friend, Paul Fegan, had just made an award-winning short film, ‘Doocots’, and was keen to have a new project.
“I would never have thought about making a film. Had anyone else asked me I’d have said no – but it shows in the film that we’re all friends and I’m very relaxed. I’d have been really self-conscious with anyone else.”
Other gigs were more successful – particularly in the north-east, where many of the songs come from and are still part of everyday life.
The pivotal moment in the film, however, was when Aidan met Sheila.
“Within 20 or 30 minutes she had asked me to sing her the song; that day we knew that the film was going to be a story about the relationship between me and Sheila.”
Dramatic, forthright, indomitable; Sheila blazed her way onto the screen – and onto the stage of the famous Glasgow Barrowlands, while Aidan was performing.
“She just said, ‘I’m not having you singing that when I’m in the room’ and no one was going to argue with her.”
It’s pure gold for the filmmaker.
“In the film, we were really having a discussion about traditional music; should you look after it, should you take it forward?” said Aidan.
“And this relationship captured everything we were trying to say.”
However, just months later came the news that Sheila Stewart had died.
“It was a shock. I didn’t suspect she was ill at all,” said Aidan.
It gives a heightened poignancy to the final film and the culture clash it captures.
They may never have agreed, but they could respect each other.
“That was her last gig. It was an amazing moment. I’m so glad we captured it,” said Aidan.
Where You’re Meant to Be tours from March 25, when the album of the tour is also released. Each screening will be accompanied by a live gig by Aidan and friends.