This is an adaptation of a classical piece
written in 1942 by the American composer Aaron Copland. It was ELP keyboard player Keith Emerson who initiated the idea, transposing the song so the keyboard was the main instrument. According to Greg Lake
, the recording came together spontaneously in the studio - as Emerson was playing the piece, Lake came in with a shuffle pattern on bass, and Carl Palmer added his drums. The engineer was rolling tape, and this first time the band played the song through is what made the album.