What do Björk, the MC5, Louis Armstrong, Oasis' Noel Gallagher and Elvis Presley have in common? Not a hell of a lot, really - but you will find all of them, through a combination of effects magic and intense behind-the-scenes wrangling, performing together in one way or another in two recent high-profile projects.

In the video for U2's latest single, "Window in the Skies", directed by Modernista! ECD and co-founder Gary Koepke, over 120 performance clips from a veritable rock almanac of artists were edited in-house at the agency and synced-up seamlessly with the U2 track (from the band's latest hits collection U218). The Mill, NY provided the invisible effects wizardry, digitally manipulating the mouths of every artist to lip-sync the lyrics.

"I came up with the treatment, but I didn't know in the end that we would have that many rights to approve," says Koepke, who estimates that there are between 60 and 70 artists featured in the clip. "I didn't know it would go up into the hundreds like it did."

Indeed, every artist appearing in the video carried a bundle of rights that needed to be cleared before the project could air - permission from the artist or his/her estate, the respective record labels, and the person/organization that shot and owned the footage.

Music archivist David Peck, president and founder of music footage company Reelin' In the Years Productions, was called in during pre-production, initially to help research the clips amassed by the agency via "thousands" of music videos and DVDs.

"I said, 'Do me a favor and send me every conceivable artist you want to see,' and from there we sent them 24 hours of material within two or three days," he says. As a result, 34 clips from Reelin' in the Years' library, culled from 30 television stations around the world and 10,000 hours of music television history, made it into the final cut. From Louis Armstrong to Frank Zappa and all points in between, Peck and his team, as well as other rights clearance experts such as Corbis, helped Jeff Estow from Modernista! business affairs make contact with rights-holders to secure the artists for the project.

Of course, not everyone wanted to play ball. "We could not get in touch with Chuck Berry at all - we couldn't find him," sighs Koepke. Other absentees included James Brown, Van Morrison and Aretha Franklin.

Edel Erickson, a producer at London's Red Bee Media, is also well acquainted with negotiating to nab the perfect shot. Red Bee was behind "Elvis", the recent BBC Radio 2 spot through agency DFGW that shows the King (circa the 1973 white jumpsuit Aloha From Hawaii era) introducing his all-star backing band, comprised of Jimmy Page, Noel Gallagher, Marvin Gaye, Stevie Wonder, Sheryl Crow, The Who's Keith Moon...and The Sugababes. Erickson says director Steve Cope went through "oceans of material" looking for the right clips and artists to include.

"It all had to fit a certain criteria," she says. "It had to look like the best band in the world, but it also had to feature artists that BBC 2 would play. It couldn't be all completely classic - that's why we went with artists like Sheryl Crow, because they were more contemporary."

Great pains were undertaken to have the footage appear consistent - everything had to come from a videotape source, which led to new footage (such as that of the Sugababes) being shot with vintage Ikegami cameras. Negotiations went relatively smoothly, with the odd hiccup - the footage that Cope discovered of Wonder on a YouTube posting came from a Sesame Street episode that could only be cleared once Grover was cut out of it. "We had a fantastic shot of Eric Clapton and he just didn't want to be in it," adds Erickson. "We spent loads of time and energy putting him in, but he was replaced by Keith Moon, so it worked out well in the end."

The biggest wrinkle could have potentially come from the Elvis Presley estate, which gave the conditional okay to use the Hawaii TV special footage but reserved the right to veto the spot if it didn't approve of the final edit.

"We were thinking that we'd done a huge amount of work that we might not be able to use because they might not let it go out," says Erickson. Having finished a final edit days before the spot was due to air, a version was sent to the Elvis Presley Foundation for the blessing of all the King's men (and women). After an agonizing wait by the phone, the word from Graceland came and all was well.

As for the U2 promo, even though it broke in mid-December ("Up to the last minute, things were going crazy" says Peck), the process of assembling its all-star band is ongoing. The Beatles - a noticeably glaring omission - were rumored to be in the final cut, but had to be pulled out by the air date. But now they're back in again, to be added to a new version airing soon. On the other hand, Bob Dylan, a man who's had Bono over to dinner, remains conspicuously absent.

"The video really made itself happen and we just tried to stay out of the way," says Koepke with a laugh. "And also make sure that we didn't put something in there like Men Without Hats."

Modernista! http://www.modernista.com
Reelin' in the Years Productions http://www.reelinintheyears.com
U2 http://www.u2.com
Red Bee Media http://www.redbeemedia.com
BBC http://www.bbc.co.uk