This instrumental, flute-based song is an adaptation of the piece "Bourrée," written by Johann Sebastian Bach. The Bach version was written for lute, and is his fifth movement of the Suite in E minor for Lute. Also known as "Aufs Lautenwercke" (works for the Lute), Bach wrote the piece in the early 1700s. The music is used for the .
In our interview with Ian Anderson he why he decided to adapt the Bach composition: "I got to the point where I was playing the flute every night on stage in the early part of '68, and so by the end of the year, I was casting around for an instrumental piece as a successor to the Roland Kirk piece, 'Serenade to a Cuckoo,' which I'd been playing most of 1968. I wanted something that had a syncopated jazzy feel, but a melody that wasn't associated with the jazz world or the blues world.
And 'Bourée' was a little bit of music that came to me through the floorboards of my bedsitter in London, because there was a media student in the room below who kept playing over and over again this refrain of the Bach tune "Bourée." He played it on classical guitar, but he only ever got the one bit, he never progressed beyond that basic thing. So I kept hearing that over and over and over and over again, and decided that I would try to use that little tune some way as a starting point for an instrumental piece.
And Martin Barre, who literally at that point in January '69 was just kind of auditioning to join the band, said, 'Oh, I know that. I think I've got the sheet music somewhere for Bach's 'Bourée.'' So it was something we could fairly readily embark upon as a variation on a classical piece of music."