The song is built over the reversed backing track of an electronic version of the then unreleased I Will (which would later be released in a much different form on Hail to the Thief).
According to Thom Yorke, in an interview with The Wire, 'We'd turned the tape around , and I was in another room, heard the vocal melody coming backwards, and thought, 'That's miles better than the right way round', then spent the rest of the night trying to learn the melody.'
To achieve the song's distorted vocals, Yorke learned to sing the vocals backwards. Then, after hearing them back, he sang the backwards vocals backwards again, giving them an uneasy sound. This technique is similar to ones used by 'The Beatles' and 'The Stone Roses' on some of their songs.
Colin Greenwood said of the vocals, 'In Copenhagen, I was listening to Woman's Hour. They were talking about this English composer, whose name I can't remember, who wrote a piece of music for a singer where all the phrasings were backward but she sung it forward. Thom sung the backwards melody. It was recorded forward then listened to backwards and he did the phrasing so as to create backward sounding words but it's sung forwards. It's kind of my favourite track'.
On Amnesiac, the song segues into the final track on the album 'Life In A Glasshouse' through the electronic noises at the start of the latter.
It also appears on their live album, I Might Be Wrong: Live Recordings.