Radiohead have gone back into the studio to start work on the follow-up to their 2007 album 'In Rainbows.'

"We just went in last week," bassist Colin Greenwood said. "It was really good. It was really noisy and chaotic and really fun."

But the group do not have fully formed songs yet, he said.

"We're at the stage where we've got the big Lego box out and we've tipped it out on the floor and we're looking at all the bits and thinking, what next?"

The new album, which will be their eighth, will again see producer Nigel Godrich work with the band.

In Rainbows was one of the most acclaimed albums of 2007, and the band shook up the music industry by releasing it on their website and asking fans to pay what they thought it was worth.

Greenwood said the band did not yet know how the follow-up would come out.

Music Journal

"We've got lots of ideas but we don't decide what we're going to do until we've finished the thing. It's all up in the air, but it was up in the air last time."

The band's only scheduled UK tour dates this year are at the Reading and Leeds festivals, which will follow festival shows in Austria, the Czech Republic and Poland.

The bassist said it was too early to say whether they would play new material at those concerts.

Greenwood was speaking at the Brighton Festival and Great Escape music conference, where he was helping to launch a new music journal called Loops, a collaboration between record label Domino and publisher Faber & Faber.

Greenwood will contribute to Loops, which will also feature writing by the likes of Nick Cave, Paul Morley, Simon Armitage and Jon Savage.

Watch Radiohead performing 'Optimistic' during a studio session below: