Mummy, I’m scared. On the stage of the Debaser Medis club in Stockholm, a woman in a sequined white leather jacket is lurching about beneath a giant inflatable eyeball. It’s not the hint of Elvis, nor the echo of Un Chien Andalou, that’s giving me the collywobbles. It’s the mask she’s wearing. It’s black spandex with an LED hot-pink trim and it encases her entire head. It’s part gimp and part Mexican wrestler, with a hint of skier-cum-predator. “I’ve got a date with the NIGHT!” she yelps into a microphone through the narrow slit for her mouth. Run, children, run!

But the rock kids of Stockholm don’t run. They cheer and pogo and sweat. They stare enraptured at the woman, at the elfin, pompadoured figure on guitar to her left (Nick Zinner), and at the upright, bespectacled, so-straight-he’s-weird drummer behind her (Brian Chase). Yeah Yeah Yeahs have come to town, and no one in this packed-to-the-rafters club is going anywhere.

The frontwoman, Karen O, can have that effect on an audience, scary mask or no scary mask. “No, it’s not too stinky,” the singer had said earlier of the skull-tight headgear that she dreamt up in collaboration with a Los Angeles costume designer. “It’s spandex, so the sweat doesn’t seep into it — it just runs down my face.” There is also the slight problem that the sweat may interfere with the battery pack powering the mask’s LED glow. Overall, she says: “It’s suffocating to wear. I’m glad to tear it off after one song.”

When you’re America’s coolest group, the band’s band, beloved of everyone from the Strokes to Depeche Mode, you don’t do many things the normal way. You make eye-blistering videos, perform roof-rattling art-punk gigs and, in the shape of third album It’s Blitz!, pump out thrillingly innovative electro-pop dance songs that pound another hefty nail into the coffin of tired old indie-guitar music. You do off-the-wall merchandise . . . forget your bog-standard tour T-shirt — anyone for a fashion wrist-cuff? You do bonkers sleeve-art — no band name or album title, just an image of an egg being crushed in a nail-varnished fist.

Yeah Yeah Yeahs don’t even do wardrobe malfunctions in the traditional manner. “At our first Shepherds Bush show in London I was wearing this outfit that was supposed to look like a parachutist’s costume,” recalls O, “but with Day-Glo paint patterns all over it. But one of the paints, this fluorescent orange, just started coming off everywhere once I started dowsing myself with water. I was completely covered in fluorescent paint by the end of the show.”

Thirty-year-old O grins her clown-wide grin — this strikingly charismatic frontwoman’s nomme de rock is short for Orzolek, her Polish dad’s second name (her mother is Korean). “That’s the kind of stuff I really like,” she says in a faltering croak full of “ums” and “likes”, her verbal hesitance accompanied by Zinner’s sotto voce mumble and Chase’s sphinx-like silence. “Those costume malfunctions — happy accidents.”

Six years ago Yeah Yeah Yeahs were the hottest band out of New York since the Strokes (Julian Casablancas and co were early champions), an art-rock trio who made an edgy post-punk, dancefloor-friendly racket that mixed up Blondie with Siouxsie and the Banshees. Their influence now can be detected in the likes of the Gossip and the Ting Tings, while their videos and tour films — some directed by the celebrated film-maker Spike Jonze — O’s former boyfriend — spoke of a top-tobottom aesthetic vision. O’s terrific range of outfits doesn’t come, as you might suspect, from some interstellar jumble sale, but from her longtime collaborator, the designer Christian Joy.

“They’re very easy to film because they have such a good identity,” says the video director and IT Crowd actor Richard Ayoade. His clip for their new single Heads Will Roll uses Karen O’s idea for a reboot of An American Werewolf in London. Ayoade, who has worked with Arctic Monkeys, says: “Karen wanted there to be some sort of creature, dancing, and instead of blood, there would be glitter. They have a strong idea of theatre.” These days O is toning down the punishing onstage rock’n’roll calisthenics that were her trademark. She’s still a hugely entertaining performer, but now the songs are doing more of the heavy lifting. It’s Blitz! is Yeah Yeah Yeahs’ great leap forward, a storming pop album that breaks free of the downtown New York scene in a manner that has so far eluded the Strokes.

Part of this reinvention is down to the band themselves. Tensions had risen between the members, with O relocating from New York to Los Angeles. The distance, and some time off, did wonders for them. As did the input of Dave Sitek, the album’s co-producer. A member of the equally hip New York outfit TV On The Radio, he’s the man who suggested to Scarlett Johansson that her album of Tom Waits covers should “sound like we drank a lot of cough medicine and saw Tinkerbell”. With Sitek’s encouragement, they downplay one of their trademark components — Zinner’s staggeringly inventive guitar gymnastics .

“Dave was like, ‘Take away all the things that you’ve spent years developing’ — all the sounds and tricks,” Zinner says.

They went for change that they could believe in. The result is a record that, midway through 2009, is a strong contender for album of the year. And Yeah Yeah Yeahs aren’t done yet. They are expected to trump sundry hoary rockers as the must-see act at the Glastonbury Festival. Later in the year all three members (but mainly Karen O) feature on the soundtrack to Where the Wild Things Are, Jonze’s long-awaited adaptation of Maurice Sendak’s classic children’s book.

“The music differs from Yeah Yeah Yeahs in that it’s tailored around Spike’s vision,” Karen O explains. “The songs are innocent and pure. We’re trying to evoke the music that would appeal to the child in anybody, and something that kids also really love.”

She’s seen her former boyfriend’s film “13, 14 times, but like 12 different versions of it.It’s pretty spectacular”, she reports. And as long as none of the monsters wears a gimp-mask, the kids should lap it up.

Yeah Yeah Yeahs play the Glastonbury Festival on June 28; the single Heads Will Roll is out on Polydor, June 29 www.yeahyeahyeahs.com

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