The guitar riff is heavy and familiar. Then - digga digga - there's that gargantuan drum break. But Kurt Cobain's throaty vocals are nowhere to be heard. Instead, a fluty-voiced 1980s pop star pipes up. It's the Stock Aitken Waterman muse Rick Astley. What's he doing here? This blend of Nirvana's Smells Like Teen Spirit and Rick Astley's Never Gonna Give You Up, entitled Never Gonna Give Your Teen Spirit Up, is enjoying heavy traffic on the web. It is just one example of the trend known as the mash-up, the recombination of disparate elements to create, in this case, an entirely new pop video.
Mash-up culture is everywhere. The virtual globe programme Google Earth was even recently spliced together with the Wii remote control to create a software mash-up that allows users to "fly" over the globe using Nintendo controls as a flight simulator. There are more than 65,000 mash-up videos on YouTube, usually posted by semi-anonymous bedroom boffins with daft pseudonyms (the Nirvana/Rick Astley video was created by DJ Morgoth). Thanks to open source software and social networking sites, commentators believe up to 25 per cent of all creative material on the web will soon be mash-ups of one kind or another.
Mash-up first barged its way into the mainstream on Feb 24 2004, when DJ Dangermouse released the Grey Album, a digital blend of The Beatles' White Album and Jay-Z's Black Album. It was an immediate hit, downloaded a million times in a single day. The Grey Video featured a digitally reanimated John Lennon breakdancing. Instead of suing for breach of copyright, savvy artists such as Annie Lennox and Limp Bizkit quickly realised the power of this new sub genre and endorsed mash-ups of their work. They recognised that mash-ups could earn them royalties without them ever setting foot in the studio. All a good mash-up needs is slick editing, an eye- catching musical combination and a sense of mischievousness.
The London duo Eclectic Method (www.eclecticmethod.net) have these qualities in abundance. The gossip website Gawker described their Michael Jackson mash-up as "the best out there". Unlike many of their peers, the duo understand pop music on a political level. Their mash-up of Beyonce's Single Ladies (Put a Ring on It) and the Confederate flag-waving, white rock anthem Sweet Home Alabama by Lynyrd Skynyrd displayed not only exquisite musical taste but also an understanding of pop music's subtexts. The footage of a 17-year-old Biggie Smalls rapping on a Brooklyn street corner set to Lou Reed's Walk On the Wild Side, meanwhile, offered two very different perspectives on New York, glued together.
While some artists such as Led Zeppelin or Rihanna feature frequently in mash-up videos, it's Jay-Z's insouciant and atonal rhymes that fit the sub-genre best. His voice has been used so often that in 2004 he sanctioned Collision Course, a mash-up album that brought him together with rap metal act Linkin Park. But Jay-Z's best "performance" is the mash up of his hit single 99 Problems and Jimi Hendrix's Voodoo Chile. It is 4.47 minutes of pure adrenalin.
Pop music's appeal frequently rests on novelty and a good mash-up revels in incongruous combinations. Since it was posted in 2006, the video of the Charlie Brown cartoon characters frugging to Outkast's Hey Ya has been watched by almost two million YouTube users. Blending Kanye West's Gold Digger with a disco version of Beethoven's Fifth Symphony sounds terrible in theory, but the video mash-up, which took just one hour to create, according to its anonymous author, is a work of screwy genius.
But the undisputed king of mash-ups is the former biomedical engineer Gregg Gillis, aka Girl Talk, who uses up to 30 tracks in a single song and whose album Feed The Animals used over 300 samples. According to Gillis, each minute of music took him a day to create. The only problem with all this freewheeling creativity? Most of the snippets of other people's songs are illegal. Gillis has argued his use of uncleared samples is fair use but The New York Times didn't agree and has described his work - and all mash-up videos - as "a lawsuit waiting to happen".
But that's another story.