Jonny Greenwood on BBC Radio 3

Jonny and Colin Greenwood spend an extended Mixing It on Radio 3 playing the records behind Kid A, a few months after it came out. The brass on “The National Anthem” began with Thom Yorke saying the song should turn into a Charles Mingus track by the end. “Thom has these ideas quite often and sometimes they're best ignored and sometimes they're genius,” Jonny says. He scored a rough tune, and he and Yorke stood in front of the players conducting, which was less Simon Rattle than jumping up and down. The last high note is played on the lowest instrument.

Finding an ondes Martenot was Jonny's teenage dream after he heard the Turangalîla Symphony, though he didn't know what one looked like; he found one, made by the inventor's grandson. It plays the notes of the vocoder Yorke sings through on “Kid A”, and the strings of “How to Disappear Completely” were first written on it. The real orchestra, John Lubbock's, recorded in the vestry of Dorchester Abbey in a freezing February, three hours with Godrich's Apple G3 and hard drive and no tape. Unlike the players on London string sessions, they came back afterwards over wine to listen, and told the brothers that a rock session, all long notes, is known as “doing balloons”.

The sample in “Idioteque” came by accident. Jonny built a drum machine from old parts, fed in records and the radio for chaos, and days later found the four notes he loved on an old competition record of electronic music, in a piece by Paul Lansky. He wrote to Lansky, a professor of music at Princeton, who liked what the band had done with his music, came to their show in New York and said that if Jonny wanted to take up the music studies he had left at Brookes, he could have a favourable interview at Princeton.

“I sort of drunkenly played other people's records over the top of what we've recorded,” says Colin, who laid Alice Coltrane over “Dollars and Cents”, a song for the next record, and Jonny wrote its strings in that style. Serge Gainsbourg's Melody Nelson, guitar, bass and drums with London session players, came to one of the brothers through a friend at Decoy Records, a record shop in Manchester, and Nigel Godrich became obsessed with its sound. They have their own studio in Oxfordshire now, which takes them back to rehearsing in village halls, “except we're not 16 anymore”.