Isobel Campbell and Mark Lanegan; When a twee pop beauty met a rock'n'roll beast

Belle and Sebastian's Isobel Campbell is on to her second album with rocker Mark Lanegan. She tells Tim Cooper about an odd coupling

Just over a year ago, Isobel Campbell and Mark Lanegan finished touring their Mercury-nominated album of duets, Ballad of the Broken Seas, and prepared to say their goodbyes. It was not a night of wild celebration: neither the garrulous Scot nor the gravel-voiced American are social creatures or party animals, and Campbell was concerned that they had reached the end of the road of their association.

"I was worried that Mark would fly back to Los Angeles and disappear into smoke, and maybe we'd never see each other again," she confesses. "I asked him that night if he wanted to make another record with me. He smiled and said: 'In a heartbeat.' And it was such a joy to see that man smile."

Lanegan is not known for his smiles. "Brooding" is the adjective most commonly applied to a man who seems perpetually to wear the long-running battle with his demons upon his glowering brow. Campbell, on the other hand, is of an unnaturally sunny disposition: girlish and giggly, the former Belle and Sebastian singer and cellist is as bright as Lanegan is dark. Which is why they made such a perfect couple on their first collaboration – and now a second, Sunday at Devil Dirt.

The age-old story of opposites attracting has always had a special place in pop history, ever since Lee Hazlewood and Nancy Sinatra got together in 1966 to sing "These Boots Are Made For Walking". The archetypal Beauty and the Beast pairing reached a climax with Serge Gainsbourg and Jane Birkin breathlessly coming together on "Je T'Aime... Moi Non Plus" in 1969. Since then, countless gravel-voiced males of uncertain age have called on ethereal younger females to cast light upon their shady mumblings, most recently when Primal Scream's aptly bestial front man Bobby Gillespie recreated another of Lee and Nancy's finest moments, "Some Velvet Morning", with the beauteous Kate Moss.

None of these, however, carries quite the frisson of the collaboration between Campbell and Lanegan. Campbell was the angelic whisper behind Belle and Sebastian's polite stylings, he the glowering beast behind Screaming Trees and Queens of the Stone Age. She was the blond, butter-wouldn't-melt Scots girl, he the monosyllabic man in black from America's rugged Pacific North-west.

Yet looks can be deceiving. It is not Lanegan but Campbell whose dark heart created the savage tales of murder and revenge that filled Ballad of the Broken Seas, and it is she who spun the seafaring yarns and dust-blown ballads on its splendidly titled successor. Lanegan might be an enthusiastic participant (though "enthusiasm" is not the first word that springs to mind), but in another sense he is merely the hired hand who brings the gritty authenticity of Americana to her lusty potion of gospel and blues, country and folk.

Campbell, 32, accepts that there's inevitably something of a Hammer Horror element to her collaboration with the 43-year-old Lanegan, conjuring clichés of the "young virgin being fed to Satan". Certainly, the vision she conjures up on one of the songs, "Shotgun Blues", is enough to have her cardigan-wearing Belle and Sebastian fans spluttering into their Horlicks. "Ooh daddy, climbing on your knee," she whispers angelically to the unseen (and, in this instance, unheard) Lanegan. "Got an itch needs scratchin',/ You take good care of me."

She also acknowledges that their relationship is a peculiar one. "It's a funny setup," she admits. "I'm not going to lie, it's very unusual. You could raise your eyebrows. I prefer to say it's a unique thing."

It was six years ago, following her departure from Belle and Sebastian, the group she had formed at 19 with her then boyfriend Stuart Murdoch, that Campbell began seeking a baritone voice for a self-penned tune called "Why Does My Head Hurt So?". Her boyfriend of the time suggested the former Screaming Trees and Queens of the Stone Age singer. Campbell had never heard of him but she subsequently sent Lanegan's record company her half-written song. "Then, a few weeks later, he called me up, having written the missing phrases, and sang it down the telephone to me."

Down the phone, at a distance of 6,000 miles, Lanegan told Campbell about himself, about his love of folk and blues, and about his hatred for the commercial aspect of contemporary music. "He is a true music fan," says Campbell, "and I honestly think that is why we hit it off in the first place." They finally met in 2003 after she went to see Lanegan play a solo show in Glasgow. "I was really moved by it and I was in the back of a car with him afterwards and he said we should make an album," she recalls. "So it was Mark's idea to do that record. And I thought it was the coolest thing anyone had said."

With both participants on opposite sides of the world – Campbell in Glasgow, Lanegan in Los Angeles – it was not to be an easy or speedy process. And geography was the least of their problems. "I would write and record the songs and send them off to him by Fed-Ex and wait for him to send them back with his parts, which was usually a matter of weeks – sometimes longer," she recalls. "Mark was in and out of rehab and he would lose the music and then find it months later on his iPod. And he felt he was letting me down, so he kept telling me I should find someone else to take over his job if I wanted."

Happily, Campbell persevered with Lanegan throughout his travails, and even managed to record a solo album, Milkwhite Sheets, during the long wait for him to complete his parts. Their resulting collaboration, Ballad of the Broken Seas, was nominated for the Mercury Music Prize, and its sequel, Sunday at Devil Dirt, ploughs a similar furrow, but with a wider palette of musical styles. The songs, vignettes that Campbell likens to scenes from a Tennessee Williams play, range from sinister tales of forbidden love set to sweeping string arrangements, to country ballads and spectral blues laments sung over scratchy acoustic guitar, mostly by Lanegan, with Campbell adorning his gravely baritone with her whispery croon.

When she began writing the songs, she found inspiration in Harry Smith's Anthology of American Folk Music, which records the earliest examples of folk, blues and country music. Another influence is the American South itself, with its melting pot of influences. "I'm fascinated by that part of the world, genuinely intrigued and inspired by it," she enthuses. "A lot of Scottish and Irish people went over there back in the pioneer days and they took a lot of the folk songs with them, and they became fused with gospel and other influences, like the Scandinavian folk music of other settlers. You can still hear mountain music that's so like Scottish traditional music and I love that idea."

Indeed, there are ghosts of Scandinavian folk tunes in the album's opener, "Seafaring Song", which Campbell wrote while on tour with Lanegan in January 2007. "I actually started writing it on a sick bag on a plane," she laughs, "and I remember writing some more in the Holiday Inn in Paris. It was inspiring having Mark around while I was writing a song for him." It was one of several songs she had already written in the hope that he would agree to make a sequel. And, after he agreed to do so in Athens, she went straight to her hotel room to burn him a CD of some of them.

"The Flame That Burns", with its rattling, wheezing rhythms and inspirational lyrics, was written not only for Lanegan, but also about him. "Sometimes," says Campbell, "he has diced with death and awful things and has been in very bad situations – some that I know of, some that I don't – and all the while I have known him, I have always been willing him to be OK."

Campbell, who plays piano, cello, guitar, glockenspiel, vibraphone and tubular bells on the album, recorded much of the music in the Catskill mountains, which imbued the sessions with their own atmosphere. "You've got the 1920s buildings with porches, you've got mountains, deer, hawks, chipmunks – a bat even came in the studio one night!" Vocals were recorded separately in Glasgow. And this time, both singers were in the same studio, Campbell having succeeded in tempting Lanegan to leave his adopted home of LA and join her in her home town. Yet she confesses: "He still kind of sung it in, even though we were in the same room. His contribution to this record was nine days in Glasgow – and mine was two years." Campbell made the most of her opportunity, too: "It was good to be able to direct him and make him sing 16 takes of every song," she laughs. "All the time I was thinking: he's here now and I don't know when I might see him again."

Despite their surface differences, Campbell insists that she and Lanegan are similar souls, united by their unsociable natures. "I'm not really an amicable person and to be with someone who sometimes doesn't say anything is really nice for me. We have an unspoken connection. Neither of us really has friends, that's what we have in common. It's not like we're buddies but we have a definite empathy. There is some kind of understanding."

Not only when they sing, but also in their photographs together, it seems as if they are simultaneously together and yet apart. Even though Campbell flew to America and donned her best cowboy shirt for the occasion, the distance between them – geographical and emotional – only seems emphasised by her cool confidence and his silent detachment, their eyes not meeting each other's, nor the camera's lens.

But there is no doubt that their collaboration is creatively fertile. "When we're on stage everything seems to make sense," she declares. "Singing with Mark feels so special to me, like a religious experience. It makes me happy. I love his voice, I love singing with him, I love writing for him, and I genuinely love him singing my songs. People don't say enough things like that these days – everyone's got an angle. What about good music?"

She adds: "He's quieter than ever these days, but I'm quite an accepting person and if he doesn't want to talk, that's fine. He may be quiet but at least he's not fake. And also," she says, "I genuinely really like him."

Isobel Campbell and Mark Lanegan tour the UK from 10 to 13 June ( www.myspace.com/isobelcampbell); 'Sunday At Devil Dirt' is released on 5 May on V2.