Northern lads: Erlend Oye and Eirik Glambek Boe are Kings of Convenience. Photo: David Sillitoe

"You see that couple sitting on the next table," he says conspiratorially. We both crane our necks to observe a stocky man in sunglasses having lunch with a smart brunette. "They look fine," Oye continues. "They could just be saying, 'Yeah, my brother's buying a new shop,' or she could be saying, 'You know what? I can't do this any more. I'm leaving in three days and I'm not coming back.' And the other person might have been planning his whole life on that person staying, so he has a broken heart inside. But you can't see it."

Actually, they look bored stiff, but you see his point. "It's really hard to tell what's going on in people's minds," concludes Eirik Glambek Boe, and he's a trainee psychologist so he should know.

You wonder what the oblivious couple would make of these two 28-year-old Norwegians if they glanced over at our table. Oye looks as if he has been designed by a cartoonist. Despite tucking into his third lunch of the day - a plate of melon and cake - he is pipecleaner-thin, with a splurge of orange hair, glasses the size of television screens and a T-shirt on which he has felt-tipped the words "Wir Jagen der Monotonie" ("We are chasing monotony"). Boe, meanwhile, is quiet and solemnly handsome. One of his hands is scarred from a wood-chopping accident; he looks the lumberjack type.

In early 2001, Kings of Convenience released their debut album, Quiet Is the New Loud, a deliciously melancholic confluence of Simon and Garfunkel, Nick Drake, Astrud Gilberto and the Pet Shop Boys. Since then, they have lived separate lives. Boe remained in Bergen, their rainy coastal home town, to study for his psychology degree, while Oye moved to Berlin where he sang with Bergen neighbours Royksopp, recorded a solo album (Unrest) and started DJing. "We need breaks from each other all the time," says Boe firmly. "It's very important."

Boe and Oye have been friends for 12 years. In previous interviews they claimed they met at the Norwegian embassy in Pakistan, or at an inter-school geography competition, but they were lying. The prosaic truth is that they shared a class at school and their first musical endeavour was a comedy rap about their gym teacher. After that they played bass and guitar in a band, Skog, who sounded "like Coldplay without a great singer".

While on holiday in Tunisia, they decided that it would be simpler to play with just acoustic guitars and harmonies, hence the name Kings of Convenience. Why decide that in Tunisia? "Because we got away from his girlfriend," says Oye. "He needed a week of concentrated music-making. It's the chemistry of our band. Boe's girlfriend, whoever she is, is always part of the band. He had two years between girlfriends and that's when he wrote most of his songs. From this period we have the foundation of our music."

True enough, Boe's current girlfriend appears on the sleeve of Riot on an Empty Street, interrupting the duo's chess game by gazing seductively at Oye her boyfriend looks glumly at the camera. It's all rather odd. "I think it sums up many things," says Boe. The chess, apparently, represents their rivalry. "It's about who is the most talented person, who's the smartest guy. We're very competitive people."

The most refreshing song on the album is called I'd Rather Dance With You, a spirited invitation to shut up and get on the dance floor. "I haven't read a single book all year," sings Oye. "And the only film I saw, I didn't like it at all." I had assumed that he was poking fun at the duo's bookish image, but he swears it's true. "Your life can be like a book or a film. I was really eager to search for the cinematic in everyday situations."

So he traded Bergen for Berlin, travelled around Europe working with dance producers and began his idiosyncratic DJ career, crooning songs by the Smiths or Pet Shop Boys over house tracks. As someone who doesn't take drugs and rarely drinks, he takes an almost anthropological interest in the dance world. "It's great to DJ for people who are on ecstasy," he beams. "You can just play any record and they go crazy and you think, Oh, I'm great. But you're not. They'll just dance to whatever."

While Boe was in Bergen, due to the pressures of touring and studying, he collapsed one day at the gym and was ill for 18 months. "When you live in a quiet little city on the west coast of Norway and you don't have anything to do, you feel like you're on the outside of the world. But it's a great place to focus your attention."

Riot on an Empty Street is a fine record - wittier and more ambitious than its predecessor. Boe calculates that it took 600 hours to record. A shame, then, that neither of them seem entirely happy with the result. "I love music like Michael Jackson that is very melodic and very well-produced, but we are not Quincy Jones," says Oye.

So you're disappointed with it? "Yes. We are always disappointed. Because we know in our minds that we could be the best."

Kings of Convenience are not conventionally ambitious. Partly, they explain, it's because their record deal is so bad that they get the same money whether they sell 10,000 copies or 1m, so why bother promoting it? They just want to be free to get on with things in their own, very different ways.

"The first thing I'm going to do when I'm not doing music anymore is city planning," says Boe."That's my number one passion in life. I'd like to hire my talented architect friends to start some housing projects in Bergen where young people can afford to live."

Oye, meanwhile, plans to keep his life unpredictable. "For the next 50 years I'll have money to do most of the things I want to do, and things I don't have money for probably aren't such a big deal." He heaves a great gangly shrug and has some more cake.