It's been called 'a triumph of postmodern reconstruction, a four-minute-19-second celebration of some of popular music's most beloved and influential figures.'

It's rare for a rock'n'roll video to find such acclaim but the treatment for Window in the Skies, directed by Gary Koepke of Boston's Modernista agency, is a class apart. We couldn't put it better than the The Washington Post: 'Elvis Presley, Johnny Cash, Billie Holiday, Marvin Gaye and a shirtless Iggy Pop take turns singing the lyrics on Bono's behalf. Instead of the Edge on guitar, you see Jimi Hendrix, Kurt Cobain, Elvis Costello and a very young Keith Richards. And hey, there's Vladimir Horowitz playing the piano! And that guy from Wilco on bass! And the manic Keith Moon on drums! All thanks to the magic of editing and copyright clearances...'

(Even though The Beatles weren't in the first edit, they are in the second edit. And in a few days we'll be premiering an even cooler version of the clip...)

With such a star-studded cast, the video has sparked feverish online discussion about who appears where and at what point. 'My favourite online comment,' says Koepke. 'Was someone asking, 'Was that Rory Gallagher at 2.37?'

The praise is all the more notable because Koepke has only previously made one rock video: 'I did one for David Bowie, in two hours flat, after we shot a TV commercial, for his album 'Slow Burn'.' In contrast this video took the best part of three months and up to 20 people. We tracked Gary down in Boston to talk about how it all came together.

When did you first hear Window in the Skies ? I first heard it back in September, we'd done a video for Product RED, a brand essence piece which explains what RED is all about. Bono shared it with the band who liked the vibe and that's how we were invited to come up with a video for Window in the Skies. I'd talked with Bono about this idea of a song that never ends, an online thing where someone starts a song and then it just continues - inspired by the Surrealists idea of the 'exquisite corpse'. I was wondering how you would get people involved in it and thinking about how we could use it for RED - it's hard to explain but it would be almost like a song that every artist has been singing for ever, where you add the lyrics but it maybe has the same chorus. Then Bono sent me Window in the Skies which was almost a singalong song itself and it got me thinking about all these artists in rock'n'roll who've dedicated their lives to their craft, to positive messages. I thought of how difficult it can be to be in a band, what a struggle it can be, of how even when you're successful you're not really sure why. Of how being in a great band is not always about training or education but more of a gift. So the thought emerged of a video that would be like U2 thanking everyone for being music fans - thanking the musicians who have inspired them.

So the initial idea about the song that never ends informed your idea for Window ?
You never know with ideas but it was in my head and I talked to Bono about this song that never ends at the same time as he was sending me 'Window'. There was an incredible moment of synchronicity: here was a song that could hold all those artists together - Radiohead and Bowie and Marvin Gaye and Elvis....

(Read the full interview on our U2.Com Subscription Site)