Jonny Greenwood

Natural habitat ... Greenwood with Radiohead. Photo: Harrison Saragossi

When a musician works outside his usual outfit for what's sometimes derisively called the ''solo project'', it's usually understood to be a way to reduce the number of people he has to report to, explain to, live with.

However, for Jonny Greenwood, Radiohead's angular guitarist, a new project commissioned by Richard Tognetti, artistic director of the Australian Chamber Orchestra (ACO), has seen the number of people he's answerable to triple or quadruple.

''I like having people to report to and work with,'' Greenwood says softly. When he became an artist in residence with the BBC Concert Orchestra in 2004, ''the first thing I did was have a printout of all of the names, ostensibly so that I knew how many players there were for each instrument. But I started getting obsessed with the names and the thought that these people weren't just presets on a keyboard.

''It's fun to be in a team and it makes it easier as well.''

Teamwork is more than just polite talk in this case because between the end of Radiohead's Australian tour last month and his pre-Christmas departure to India and then home to England, Greenwood spent several weeks in intense workshops with the ACO.

What Tognetti calls ''every composer's dream to have access to live musicians'' during composition was a rare chance for composer and orchestra to bat ideas back and forth. It has resulted in Greenwood heading home with rehearsal recordings, an annotated score with notes from each player and fresh ideas on how to approach the still unnamed composition that is to become part of the ACO's touring repertoire in 2014.

''The workshops have been a whole series of finding things that can't be done and ways that it can be improved and explanations of what would make it better,'' Greenwood says. ''How else am I going to learn this stuff?''

With his non-rock work mainly being as a film composer (The Master, There Will Be Blood) along with the widely played chamber piece Popcorn Superhet Receiver, which the ACO performed in 2010, Greenwood describes himself as still learning his craft. But it is with the ''healthy arrogance that comes from being mildly ignorant of how these things are done … and the weight of things that have been done''.

However, Tognetti has little doubt the Englishman is no musical dilettante, declaring: ''Jonny's technical skills, they are up there with any other composer I've worked with.'' The art of commissioning is ''identifying someone with a genius, like Jonny, but making sure we have the right circumstances''.

Together in a room you can see that the violin-playing surfer from Wollongong and the pale ondes Martenot player from Oxford have a few things in common, beginning with their reluctance to be in the spotlight. Greenwood disappears under his floppy fringe before the camera and Tognetti physically recoils from the recorder as the interview begins.

There was also a musical language they had in common when this process began, an eastern European connection that crosses at many points, including the Polish composer Krzysztof Penderecki, whose Threnody for the Victims of Hiroshima is a core text for Greenwood.

''I go to Slovenia every year and you walk or drive over the border from Vienna and there is something about the [eastern European] character,'' Tognetti says. ''I was really surprised when I heard Superhet all those years ago and realised that Jonny was tapping into eastern European classical music, which are some of my absolute, most heartfelt favourite sounds; all the way back to Dvorak and Janacek and, of course, Penderecki.''

There's another language they share: an appreciation for the inherent appeal of music played live by flesh and blood and not machinery.

''Xenakis said something really interesting - being an amazing mathematician and an architect and writing really strict mathematical structures - that it was the idea of people making slight errors that is the beauty of playing in a live orchestra,'' Tognetti says.

Greenwood nods, his fringe bouncing. ''I spend so much of my time hearing speakers and I still love programming laptops, and that's an exciting sound world. And yet hearing something like Pederecki's First Symphony in a room is the strangest sounds you can get.''