For the Knife to be any more enigmatically Swedish, they would have to come with illustrated instructions and an Allen key. Karin Dreijer Andersson and her little brother Olof Dreijer don’t like to show their faces in photographs, so they wear masks. They’re so averse to playing live that despite forming the Knife in 1999 and recording three albums, they have only made three concert appearances. And, as I’m about to find out, they treat interviews like dental appointments.

The fourth gig of their career is around five hours away when I meet them at Scala, a club in King’s Cross, London, that holds over 1100 people. We adjourn to a glassed-in bar area overlooking the main room, where sound-check is about to take place, and two gigantic dummies with oversized heads and no faces are being wheeled on stage.

“They will have faces projected on them,” Olof explains. “They will move. And they will sing. You will see tonight.”

Karin was born in 1975; Olof in 1981. Because of the age difference and the fact that Karin left home when she was young, the two didn’t have much to do with each other. At home their father played guitar, accordion and trombone, and let them play all his records.

“But ABBA was not allowed at home,” Olof is quick to point out.

“He had Miles Davis, Bob Marley, Jean-Michel Jarre,” adds Karin, who speaks quietly, but not quite as quietly as her brother.

Karin had been a member of Honey Is Cool in her early twenties, an indie guitar band inspired by Sonic Youth and The Pixies. Olof was into free jazz and playing saxophone. Coming together as The Knife, they create an arty-yet-catchy pop-electronica with squelchy synths, pristine beats, and Karin’s voice spookily veering between a low Nico moan to a high Kate Bush squeal. Sometimes her larynx is manipulated to sound like a man. Their biggest commercial moment so far has literally been a commercial. Their 2002 song “Heartbeats” was covered by fellow Swede Jose Gonzalez and used in a popular TV ad for Sony high-definition televisions.

“That was a very hard decision,” says Olof, after furrowing his brow for ten seconds. “I haven’t thought about it enough to know if I regret it, but at the time we needed the money. That’s not necessarily a valid argument, but we were able to use it to pay people at our label decent salaries, and put it towards our live show.”

The siblings are fiercely independent and opinionated. They release their albums through their own label, Rabid. When they won a Grammi (a Swedish Grammy) for best pop group in 2003, they got two performance artists to accept it for them wearing gorilla masks and shirts bearing the number 50, to protest the fact that the male/female ratio in the Swedish music industry should be half-and-half. And then there’s the reticence to show their faces. For photos associated with their latest album, Silent Shout, which is darker than their previous work, they have large beaks strapped to their faces. 

“When I buy a book, I don’t want to see how the writer looks,” says Karin. “So why do we do that with the people who make music?”

The performance that night is a cross between theatre of the absurd and a nightclub nightmare directed by Devo and David Lynch. Olof and Karin walk onstage in black body suits and creepy skin-tight facemasks, obscured by a translucent screen on which multilayered images are flashed in semi-darkness. The surround-sound system ensures that the songs are felt in your bones as well as your ears. The crowd goes nuts. Not that The Knife really care about that. They don’t say one word all night.

“The feedback you care about is from other musicians you like, or friends you are close to,” Karin said earlier. “But when you get feedback from a thousand people at a time, I don’t really know how to react to that. When we make music, it’s like we’ve created this world and these characters. It’s not us.”

“It’s like theatre,” says Olof. “It’s not reality.”

“Yes,” says Karin, nodding at her brother. “It’s a game we play.”