Psych-pop wonder Cate Le Bon has a way with commemorative words.

"I forget the detail, but remember the warmth," she sings on Mug Museum, the title track from her current album.

The Welsh singer-songwriter wrote the LP in the wake of the death of her grandmother, and it gently yet profoundly explores relationships, loss and familial roles.

Its songs are wonderful in their own right - Le Bon's garage-folk chanson is mesmerising - but they're set to find a new lease of life thanks to a film about (and love letter to) Glasgow from Turner Prize-nominee Phil Collins, which premieres in the city tomorrow.

Entitled Tomorrow Is Always Too Long, Collins' ambitious undertaking celebrates the lives of Glasgow's people - its children, pensioners, in-patients and prison inmates - and is the product of a year spent in the city's institutions, from maternity hospitals to care homes.

The film, which will be screened in Queens Park's Rose Garden, was commissioned by Glasgow's Common Guild gallery and shot by Michael McDonough (Winter's Bone). Part of the Glasgow 2014 Cultural Programme, it features scripted vignettes by Ewan Morrison, and a soundtrack courtesy of Mogwai's Barry Burns, local groove-pop deviants Golden Teacher and Cate Le Bon - as arranged and performed by the Royal Scottish National Orchestra, and sung by Glasgow locals.

Le Bon and Collins first met three years ago. They were introduced by her Welsh pop ally Gruff Rhys (Super Furry Animals), with whom Collins collaborated in 2011. "I was absolutely arrested by Phil's work, it's incredible," says Le Bon of the Berlin-based visual artist, who has previously staged a disco marathon in the West Bank and made a film about anti-fascist Malaysian skinheads. "He manages to tread what could be a very treacherous path, but he does it with such compassion and beauty."

The feeling was mutual. "Phil's always been vocal about the fact that he's a fan of my music, and he said he loved Mug Museum," recalls Le Bon. "Then one day I got this text from him which said, 'I really need to speak to you. I need to ask you something'. That sounded quite daunting. But then he phoned and said he thought that the songs from the album would be the perfect soundtrack for Tomorrow Is Always Too Long, and would I mind if he gave them to the Royal Scottish National Orchestra to orchestrate." She laughs. "Would I mind! I said of course. It's such an honour to hear your songs being played by this incredible orchestra, and then for them to be incorporated into a Phil Collins project. It's one of the best things, career-wise, that's ever happened to me. It would take something epic to eclipse it."

Collins, whose father was from Glasgow, cherry-picked songs from Mug Museum for the project, in which he asked locals to sing and dance, among other adventures. "He chose around seven songs from the record, and then worked with an arranger, who I did a bit of back and forth with," says Le Bon. "Then the Royal Scottish National Orchestra recorded them, and Phil got different characters from the different establishments from within Glasgow to sing their versions of the songs."

How did it feel to hear strangers interpret her songs, especially given they had such a personal, familial resonance to Le Bon? "I'm trying to remember what song he sent me first," she says. "I think it was Duke, and it gave me goose bumps. It's quite shocking hearing someone else interpreting your song in a way that you've never thought of before, even though it's come from your mind. He kept sending them through, and each one was surprising. There are particular songs that have really got me - there's a 10-year-old year singing No God, which is really powerful. That reduced me to tears."

She continues: "I think after the process of making a record like Mug Museum, and being on the road with it for so long, you kind of detach yourself from it, and what the songs meant to you at the beginning - so having Phil do this with them has been really lovely for me, I've reconnected with that side of the creative process."

Has Le Bon heard her fellow musicians' contributions? "No, but I saw Barry [Burns, Mogwai] at Glastonbury - I think he's seen a lot more of the finished piece than I have - and he was wildly excited by it all," she says. "It's just an absolutely wonderful thing. I'm still blown away that I'm a part of it."

Will she be at the screening this weekend? "Oh yeah, and I'm bringing my mum and my aunty up too. Some of these songs were written about their mother. I guess we might need some tissues."

Tomorrow Is Always Too Long, tomorrow, Queens Park, Glasgow; Cate Le Bon plays Aberdeen Lemon Tree on Sept 14, Edinburgh Electric Circus on Sept 16 and curates her own festival, Mas Mas, in Wales on Aug 28.