Peter Bjorn and John, Forum, London<br/>Super Furry Animals, Roundhouse, London

Faceless advertising executives have made minor stars of an obscure Swedish trio. Meanwhile, it's business as usual in Wales

Who are the most powerful people in pop in 2007? It isn't the DJs any more – who actually listens to the radio? It isn't the journalists any more – who actually reads the press? It isn't cat-stroking, cigar-chomping svengalis either – give or take the handful who hog our television screens on a Saturday night, they're a dying breed.

The real power brokers are the people you've never heard of: the entry-level BBC employees who source the music for trailers, and the pen-twiddling advertising execs who idly scroll through LastFM looking for something hipster-cool to associate with the latest product. The whims of these new gods can make or break a career. Take the case of Peter Bjorn and John, the Swedish indie trio who had been rolling along modestly, accruing moderate critical acclaim, until their single "Young Folks" caught the attention of the faceless deities.

Since being used by – and this is an abbreviated list – Grey's Anatomy, Chanel, AT&T, Budweiser, Napster and Fifa 08, "Young Folks", which was originally released in 2006, has been reissued and become one of the songs of 2007, with the knock-on effect that with Writer's Block, their third album (as is mysteriously the case with Scandy bands), PB&J have made a British breakthrough.

Consequently, Peter Moren (vocals, guitar, harmonica, and the talkative main man, although they duet in different permutations according to the song), Björn Yttling (vocals, bass, keyboards) and John Eriksson (drums, vocals) find themselves facing big audiences such as tonight's who know them for just one track.

Which is a pity, because the rest of their material is quietly lovely, in the way that twee, Swedish indie often is. "Young Folks" itself, though mortally overplayed, is a lovely thing too, with that shuffling beat and those Roger Whittakeresque whistling bits. It's a song about trepidation, deliberating over how a prospective new lover would react if they knew about the guy's past. Tonight, she is played by a check-shirted and boyish Robyn, doing the part of Victoria Bergsman (the ex-Concretes singer whose vocals are on the original). After which, an apologetic exodus begins. It's Sunday night, and tomorrow morning there are products to be sold, programmes to be trailed...

"What's so good about them, then?" When somebody asks me why I'm so excited to be seeing Super Furry Animals at the Roundhouse, I'm temporarily stumped (a bad sign for someone in my profession). My love for this band runs so deep that it's almost pre-verbal. And, on the surface, SFA aren't easily explained as candidates for fan-love: five Welsh stoners in their 30s (and, in one case, 40s) with woolly hats and fuzzy faces. "Stop! Said the puppy..." (from "Golden Retriever") is one of my favourite lyrics, but even when I home in on specifics, it's hard to say just why.

It's just that, if, say, "Run Away" (the new single from the Hey Venus! album), or "She's Got Spies" (the two-speed classic from their masterpiece Radiator), or "Northern Lites" (their salsa beauty performed tonight in the style of Hüsker Dü), or "Rings Around the World" (the cosmic boogie juggernaut from the album of the same name) or "God! Show Me Magic" (their Buzzcocksian debut single) fail to bowl you over, I'd get a doctor to do an X-ray search for your heart.

SFA mix the gentle British (one is tempted to say English, but it wouldn't be right) surrealism of Milligan and Lear with the cannabis counterculture of Cheech & Chong, and the iconically cool (Brian Wilson, Lee "Scratch" Perry) with the criminally uncool (Electric Light Orchestra, The Moody Blues) to create a sound which causes in the listener a woozy warmth, a benign fever, a happy flu.

Plus, the voice of Gruff Rhys is nothing less than a national treasure. Tonight, he's in raconteur mode, explaining how he came to own 50 Cent's special platinum microphone: "It wasn't special enough, so he sent for a diamond-encrusted one from America."

Then, before the Barry White pastiche of "Juxtapozed With U", he nails SFA's peculiar appeal better than I ever could. "We're a band who like to hang out in dangerous places. And the most dangerous place to be is the middle of the road ..."

Further listening Find out where to hear more Swedish pop in London at myspace.com/tacktacktack