From the outside, it looks like any sleepy suburban house in the canyons of Beverly Hills, miles from the glitz and grime of downtown Hollywood. Inside, however, the walls and tables explode in a Pop Art riot of garish memorabilia, Russian dolls, Pacific island paintings, autographed cereal packets and multicoloured rock’n’roll relics. This is Russell Mael’s accumulated flotsam from four decades as half of pop’s oddest couple, Sparks.

This Willy Wonka-style pop factory is not only Mael’s home but also a rehearsal studio for Russell and his older brother Ron. Cordial and droll hosts, Sparks appear spookily trim and ageless. Given their alleged birth dates, they could plausibly be from another galaxy. The boyish singer Russell is reportedly 58, the keyboard player and songwriter Ron is 60. Both could easily pass for 15 years younger. But that’s only in Earth years, of course.

Longevity is clearly a Sparks forté. During their four-decade career the Maels have been both leftfield chart-toppers and avant-pop outsiders. But even in the lean years they attracted critical acclaim and famous fans, from Andy Warhol to Beck, Björk and the Pet Shop Boys. Erasure and Justin Hawkins, formerly of the Darkness, have covered their songs. More recently, Franz Ferdinand suggested collaborating.

Not forgetting Morrissey, of course, a longtime champion of Sparks who used to pop over when he lived in LA. “Our only disappointment was that he didn’t draw up in a horse and carriage,” Russell sighs. “It was a Jaguar XKE.”

“I’m sure his horse and carriage was just being reshod,” Ron dead-pans. “It was in the blacksmith’s that day.”

Morrissey invited Sparks to join his Meltdown festival lineup in 2004. Now the Maels have belatedly repaid the compliment, in a backhanded way, with a song called Lighten Up, Morrissey on their shiny and sardonic new album, Exotic Creatures of the Deep. Despite its arch title, the song is really a plea for a potential girlfriend to cool her obsession with pop’s most famous celibate vegetarian.

“We gave it to Morrissey about two weeks ago and he’s in love with it,” says Russell. “We wanted him to hear it before it got out there.”

“It could have gone either way!” laughs Ron. “There is some humour in telling Morrissey to lighten up, but I would hate it if he ever did, because then he wouldn’t be Morrissey. He would just be . . . one of us.”

Another standout track on the album is a sleazy, sarcastic electro-glam stomp called I Can’t Believe that You Would Fall for All the Crap in This Song. A very Sparks confection, it is a seductive pop tune that sneers at seductive pop tunes.

“It’s directed at a person who would fall for a generic saccharine expression of love in a song,” Ron says. “Too much pop music is so lyrically generic. Getting back to Morrissey, I don’t hear too many threats to his lyrical supremacy. He is definitely Attila the Hun in that regard.”

Having revisited their 1974 album Kimono My House in full at Meltdown, Sparks are now taking the vogue for single-album revival concerts to record-breaking new extremes. In London, from May 16, they will play all 21 of their albums to date, in full, including the new one. That’s 250 songs or, if you prefer, 4,825,273 notes. Imagine a West End musical in which the score changes every night.

“Exactly,” Ron grimaces. “It’s a real test of how many brain cells are still left. There are quite a few songs that not only have we never played live before, we don’t even remember writing them.”

“It’s something very few people could do because very few people have that big a catalogue,” Russell says. “And the ones that do probably wouldn’t want to take the time. It’s way too much work. Mick Jagger would not do this project, I guarantee you.”

Clearly, unlike most bands, age has not mellowed Sparks but made them even weirder. While their early albums were relatively conventional glam-pop affairs, they later put their sideways slant on disco, techno, orchestral pomp-rock and Broadway-style big-band ballads. The Maels were postmodern before the term existed.

Likewise their live performances. While their London marathon will begin with fairly straight rock shows, the latter albums are being presented in the surrealistic cabaret style that has become their trade-mark. More Reeves and Mortimer than Pet Shop Boys, Sparks shows are grand, witty, slightly unhinged spectacles.

Although they have enjoyed commercial success on both sides of the Atlantic during differing stages of their career, Sparks decided to mount these concerts as a one-off series in London only. “London has always been really supportive of Sparks through the years,” Russell says. “So we thought that if we were going to do it just in one city, where would be the best?”

Indeed, Sparks have long enjoyed a special relationship with Britain. Die-hard Anglophiles when they formed in 1968 under the name Half-nelson, they initially proved too weird for America in the preglam era. So they changed their name and relocated to London in 1973, where their stylised mini-operas made much more sense alongside the arty histrionics of David Bowie, Roxy Music and early Queen.

With huge hit singles such as This Town Ain’t Big Enough for the Both of Us, England embraced them, despite their scary Top of the Pops appearances, notable for Ron’s dead-pan scowl and sinister toothbrush moustache. A twisted homage to Hitler, most Brits believed. Not so, says Ron. “It doesn’t sound genuine to say but it really wasn’t,” he says. “I thought of it more as a kind of silent-movie badge. Laurel and Hardy, Charlie Chaplin, that was the direction from my point of view.”

Ron now sports a more dapper pencil moustache. Until recently, his original facial furniture was displayed at the Hard Rock Café in Los Angeles. But the restaurant closed down and the priceless hairy relic mysteriously disappeared. “Who knows, maybe it’s on eBay,” Ron muses.

Raised in suburban LA, the Maels had no special training for pop fame. Their father was a painter and newspaper art director, their mother a school library administrator who first encouraged her sons into showbusiness by becoming child catalogue models.

“She was a stage mom, or whatever you call it,” Russell says. “A catalogue mom. It was pretty low-end. No, it’s not embarrassing. We’re proud of our heritage.”

The Maels guard their private lives carefully. Russell confirms that neither he nor Ron is married and neither has children. But he refutes the implication in many profiles and interviews equating their androgynous, theatrical image with being gay. “We’re not gay . . . as far as we know. Ha!” Russell laughs. “No, we are not gay.”

“People are surprised,” Ron says, “because it is said or implied that some of the bands that we are kind of linked with – er, not romantically – are gay. I don’t know what it is, there is just a flamboyant nature to what we do. A nongay flamboyance, I guess.”

Ron even bristles when I describe Sparks as “camp”, arguing that the term implies dishonesty and detachment. They may be brothers from another planet, but the Maels do not want their musical mission to be misunderstood.

“We’re genuine in our own way,” Ron protests. “There is a sort of pose to what we’re doing, but it’s a natural pose. A heightened version of what we are when we’re not being Sparks. There is irony in what we do, but not to the point that we feel we are outsiders working within pop music. We really love pop. That’s the reason we keep doing it.”

Sparks play the first of their 21 concerts at Carling Academy Islington, N1 (08444 772000) on May 16 2008. Exotic Creatures of the Deep is released on May 19 2008 by Absolute

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