JULIE Fowlis, says Alex Mandel, is a "wonderful, amazing singer" with an "incredibly clear, precise quality to her voice." He may have come slightly late to the Fowlis appreciation party, but his verdict is important nonetheless.

Mandel is the multi-instrumentalist who wrote Into the Open Air and co-wrote Touch the Sky, two stirring songs performed by Fowlis on the soundtrack of the latest Disney/Pixar smash, Brave. The film opens in Scotland on August 3 on the back of a remarkable wellspring of publicity – not to mention $250 million (and counting) in global box-office receipts. Not bad for an animated feature that was only premiered in Los Angeles on June 18, and in Edinburgh and Inverness less than a fortnight later.

The story has been told how the film's creatives listened to piles of Gaelic albums and kept returning to Fowlis's. The phone call, from music supervisor Tom MacDougall, came utterly out of the blue. Mandel worked with Fowlis and her team by email – she recorded her vocals at Castlesound Studios, a studio housed within a 200-year-old primary school at Pencaitland, outside Edinburgh, and the results were emailed to the States. Composer and singer didn't actually meet until the premiere in Hollywood. Understandably, Mandel has said it was "pretty surreal" to collaborate with someone he had never met. "But it worked out really well," he adds.

A spine-tingling moment at the Edinburgh premiere came when Fowlis (resplendent in an outfit co-designed with her friend, the couturier Sandra Murray) and three musicians played the songs from Brave. She was accorded an emotional reception.

"It's a fantastic film, we loved it," the 33-year-old says now. "We first went out to see it in the new Dolby Theatre in LA, which was an amazing experience. As great as that was, however, it was equally brilliant to sit and watch it with a Scottish crowd in Edinburgh. The reaction to the film was very positive but there was a different reaction to bits of humour in the film. There were a lot of hearty laughs in the Edinburgh crowd – some of the in-jokes might have gone over the heads of the American audience but they were very much appreciated here.

"But it does look amazing. It's a beautiful representation of Scotland in terms of its landscape. The Scottish environment comes through bright and shining – the lochs and the sea and the colours of the mountains; all these greens and browns."

The detailed look extends to the red curls of Merida, the film's engaging central character. "I don't know much about the technical in and outs of it all," Fowlis acknowledges, "but I do know they had to develop new technologies to get her hair to look the way it does."

How did she feel about her own contribution to the soundtrack? "We were very pleased with how it came over. Patrick Doyle's score is wonderful. The songs I did were worked out separately from Patrick's score. I like the way the soundtrack flows flawlessly from the songs to the score and back again. The Disney/Pixar music team's attention to detail is phenomenal. I had a real sense of that working with them. Every note, little nuance, every word was considered carefully before it was given the stamp of approval. I enjoy working like that – spending the time in order to get something right."

By a quirk of fate, while working on the songs she received another call from the US, this time from a department responsible for advertising and trailers. They wanted to use a track from her 2005 debut album, Mar a Tha Mo Chridhe [As My Heart Is], in the TV campaign for Brave. "They picked out a lovely slow song called My Love Is In The High Seas. The TV campaign was launched during the Oscars to an audience of about 40 million, which is probably one of the biggest audiences for Gaelic song ever."

It was four years ago that Fowlis was described in an admiring Guardian profile as "North Uist's biggest celebrity, this year's BBC folk singer of the year and the best-known Scottish Gaelic singer on the planet." Music and song were appreciated on both sides of her family, her mother's family all spoke Gaelic, and Julie was still at primary school when she sang her first traditional Gaelic song. Later, she came to Glasgow to study music at Strathclyde University.

She studied Gaelic at Sabhal Mòr Ostaig, now part of the University of the Highlands and Islands, and this led to her finding a place in the Gaelic group Dòchas, with whom she toured and recorded, showcasing her instrumental skills. In 2005, she released her first album and also won the title of Gaelic Singer of the Year at the Scottish Traditional Awards.

To read the English translations of the Gaelic lyrics on her three striking, and increasingly well-received, solo albums – her debut was followed by Cuilidh (2007) and Uam (2009) – is to be struck forcefully by the sense of history and community that runs through them. One celebrated song concerns the "Raiders" – island men who returned from the Great War but failed to receive the land they had been promised in return for signing up. One group of men responded by raiding the land they had been pledged. Other songs in Fowlis's canon have plainly been handed down through generations.

"That is partly a Highlands and Islands thing and partly it's just part of folk culture," she says.

"You'll find with folk songs in any language that they are shared in communities and families and handed down from one generation to the next. There's a real sense of the unbroken line and the oral tradition. Certainly, in the island communities, a lot of the Gaelic songs I sing on the albums have been passed onto me by tradition-bearers – people I know, family members, friends of the family. Most of them are highly meaningful to me in that sense. Some have been learned from archival recordings."

The singer has just been appointed artist-in-residence at Tobar an Dualchais, the digital Gaelic and Scots archive, a remarkable resource of some 26,000 oral recordings covering everything from stories and songs to poetry amassed since the 1930s. Some of the stories were recorded on wax cylinders in 1937.

"It's an incredible achievement to have all these recordings online," she says, adding that the post will allow her to seek to develop musical projects from the archive.

Fowlis, who last October obtained an MA in Material Culture and the Environment from the University of the Highlands and Islands, is also proud of Heisgeir, her intriguing multi-media project about the now-unpopulated Monach Isles, which was acclaimed at last year's Blas festival in the Highlands and at January's Celtic Connections.

"It was a great project to work on, and the first thing I've ever really done in that vein. It was a very steep learning curve, but one I enjoyed. I would like to develop the project further but there's been so much going on that I haven't yet decided what the next move is, whether it's as a TV programme or an album. It's still a work in progress." She and her band performed Heisgeir twice last week, in Stornoway and on Skye. Needless to say, it went down exceptionally well in both locations.

The good news is that preparatory work has started on a new album. "We're just getting the beginnings of all that together now and are looking to record over the winter. We've had such a busy time these last five years – touring, and playing festivals – that I'm enjoying taking a little time out and being creative.

"Working on the Heisgeir and Disney projects, getting the music out there is different ways, has been energising, and it makes me ready to look at a new album."

The two songs in Brave were both in English. Would she record other songs in the language? "I've never been one to say I wouldn't do it. My real passion is Gaelic singing, but as far as English concerned, we'll never say never."

Next week will find her presenting coverage from the Cambridge Folk Festival for Sky Arts, alongside Mark Radcliffe and Zoe Ball, and there's also a major new series in the pipeline for BBC Alba, on music from Scotland and Ireland. She plays the Perthshire Amber Festival in October, plus has two dates in Germany and one in Switzerland in November. As if all that wasn't enough, she recently gave birth to her second child.

More immediately, Brave will broadcast her name to new audiences. Several of Alex Mandel's followers on Twitter have already said how much they like the soundtrack album – and his songs, and Fowlis's voice, in particular. The appreciation party is about to get a lot bigger.

www.juliefowlis.com Gaelic digital archive: www.tobarandualchais.co.uk

Brave (PG) opens in Scotland on August 3.

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Teal Holyrood tartan (by Lochcarron of Scotland) tulle kiltdress and lace fingerless gloves, price on application, Sandra Murray. Fishnet tights, from a selection by Fogal. Earrings, from a selection from Pellini. Gold metallic wedges, from a selection by Terry de Havilland

Make-up and hair: Michelle Coletta

Thanks to Ali and Martin Watson at Drynie Farm, Dingwall.

Stockists: Begg Scotland (www.beggscotland.com); Fogal (www.fogal.com); Iona Crawford (www.ionacrawford.com); Joyce Paton (www.joycepaton.com); Pellini (www.pellini.it); Rosie Sugden (www.rosiesugden.com); Sandra Murray (www.sandramurray.com); Terry de Havilland (www.tdhcouture.com); Wolford (www.wolford.com)