Instead, Pummell would send Greenwood half an hour of footage that was about to be edited down to 10 minutes, so that he could get an idea of the intended mood; Greenwood would send back 15 minutes of music, and the two elements would expand or contract as required until they fitted.The open-ended brief allowed Greenwood freedom to explore some unusual, even arcane, techniques and instruments. "It's the most expressive electronic instrument that's ever been invented, I think, just so natural to play - neutral in a way, but so magical." A curious instrument akin to a more sophisticated theremin, the ondes martenot has several unique features, including a speaker strung with resonating strings, and an ingenious pressure-sensitive button allowing infinite control of a note's attack. So there's no repetition in it."Their working relationship was much freer than in most movie projects, which usually involve the composer working to millisecond tolerances to fit music to a finished scene. Instead, I could just do three or four minutes of music in whatever mood, and people could play in free time - and occasionally, Simon Pummell would even edit the film to the length of the music, which was a real luxury."The trouble with that freedom was that I couldn't really repeat themes, as you can in a traditional film - because obviously, the music for someone giving birth wouldn't sound great being reprised for a shooting or a fight later on.

It was great not to have to leave room for dialogue, and not to have the musicians playing to click-tracks, just so they could fit in exactly with a car chase or what-ever, which I guess is true of traditional film music. "There was a lot of music to provide: the film doesn't have any dialogue in it, just music and images for an hour and 20 minutes. "It was done in the same studio, with all the same instruments lying around, and some of the techniques we learnt for those albums are reproduced here, I'm sure," he says. Plus the idea of all this film just mouldering away, finally being seen.

There's going to be a website where, once you've seen the film, you can research the clips and find out the history behind them. He's polite and attentive, appreciative of any interest in his work, and eager to inform."My take on the film is that Simon has basically gone and visited lots of film libraries around the world and dug out material that relates to various themes he's chosen to do with human experience, for want of a less pompous phrase," he explains. For instance, there's one really strange clip from Thirties Germany of two toddlers dressed as Nazis, carrying Nazi flags and playing drums, and you can read about how they grew up, and what happened to them."Having pitched a few ideas to the director, Greenwood set about creating pieces to fit various sequences with Graeme Stewart, the engineer on the Kid A and Amnesiac sessions. The way he described it to me at our first meeting was that originally, the whole point of filming a moving image was to record what's going on around you, and this is the kind of film that should be made more often, which I found interesting. "The result is that he's got footage from the turn of the century of people dancing, next to anthropological films of dancing around the world; and he's got scientific film from the 1960s of eggs and embryos, in a kind of collage thing.