What did Thom Yorke play on Band Aid 20's “Do They Know It's Christmas?” in 2004?

The song opens on piano before Chris Martin's first line. Jonny Greenwood played guitar, Paul McCartney bass and Supergrass's Danny Goffey drums, at Air Studios on 13 and 14 November 2004, with Nigel Godrich producing. Neither Thom nor Jonny sings a line.