He claims to be the lover of Janet Jackson and Mariah Carey, but Gnarls Barkley doesn’t do things by halves. His record Crazy has become the first single ever to make the top of the charts in Britain on the strength of download sales alone.

The person Gnarls Barkley does not exist except as the alter ego of two American anglophiles who conceal their identities behind promotional photographs showing them in bowler hats and mascara in the style of A Clockwork Orange, further enhanced by blond wigs and large nappies.

This can be a disturbing sight given that one half of the goofy partnership, the black vocalist Cee-Lo Green, aka Thomas Calloway, weighs nearly 20 stone and has a bald head tattooed with the word “Trill”, inviting speculation about a sponsorship deal with the maker of budgerigar seed. Trill also describes his voice, which evokes Barry Gibb of the Bee Gees.

His sidekick, the hip-hop producer Brian “Danger Mouse” Burton, is no less disconcerting, particularly for the record company EMI which served “cease and desist” orders on him for mixing the Beatles’ White Album with The Black Album by rapper Jay-Z to create The Grey Album in 2004. Although never officially released, it was an underground sensation and won Burton a Grammy nomination.

Gnarls Barkley’s single Crazy, not to be confused with the song by Patsy Cline, has been hailed by critics as a superb, innovative tune with a taut, punchy bassline, soaring vocals and a massive singalong chorus. It has deposed the troubled Babyshambles singer Pete Doherty from the front page of the New Musical Express and is played endlessly on Radio 1.

It is also a triumph for legally downloaded music. So many fans paid to download the track from the internet that it eclipsed all other record sales, notching up more than 31,000 in five days. Their new album, St Elsewhere, is expected to go straight to number one when it is released on April 24.

Until recently, download sales only counted towards a chart position if the record was available in stores, but the rule has been relaxed by a proviso that copies must be in the shops within a week. The Arctic Monkeys recently put out Britain’s fastest selling number one album ever after fans heard their music on internet sites.

At which point, an older generation could be forgiven for murmuring, “Oh gawd — internet downloading, another fictional artist — roll on, bleedin’ death.” But that would be to miss a rich bit of schadenfreude. The success of Gnarls Barkley is proof that the internet has played a cruel trick on the young by depriving them of a hallowed tradition: despising their parents’ music.

It works like this. Immersed all day in their music websites, the poor dears are bombarded with messages that wheedle, for example: “If you like this you’ll also like Long Tall Sally by Little Richard.” Naturally, they don’t know Little Richard from Keith Richards or even Cliff Richard, but the chances are they will try it and perhaps recommend it to their friends. Fashions, eras and genres have become irrelevant.

The result is that savvy teenagers are listening to Jimi Hendrix and back catalogues of the classics from the 1960s and 1970s. The record companies, while petrified by the internet, can’t believe their luck at this potential windfall.

“The rite of passage of rejecting the past has changed,” says our rock writer Dan Cairns. “Today's internet generation spend all their time cross-referencing, dipping into the musical past while embracing the musical ‘now’. They listen to everything because it’s available. They have the equivalent of a massive vinyl collection on their iPods.”

Gnarls Barkley meshes precisely with this trend. Their music is a free-wheeling mixture of funk, soul and hip-hop, carrying the sonic references of James Brown, the Temptations, Marvin Gaye and the Beach Boys but tweaked with new technology and sounding cumulatively like none of them. By any standards it’s highly rated stuff. Calloway and Burton have been hailed as two of the most original talents in popular music.

So why hide behind a virtual persona with an excruciating name? It’s perhaps no coincidence that Burton worked with Damon Albarn, the Blur frontman who helped to create Gorillaz, the British virtual band represented by animated Japanese cartoon characters. Madonna “danced” with them at the Grammy awards recently. Burton’s work on the Gorillaz album Demon Days earned him another Grammy nomination.