 Lennon composed " Imagine " one morning in early 1971 , on a <unk> piano , in a bedroom at his Tittenhurst Park estate in Ascot , Berkshire , England . Ono watched as he composed the melody , chord structure and almost all the lyrics , nearly completing the song in one brief writing session . Described as a piano ballad performed in the soft rock genre , the song is in the key of C major . Its 4 @-@ bar piano introduction begins with a C chord then moves to <unk> before changing to F ; the 12 @-@ bar verses also follow this chord progression , with their last 4 bars moving from Am / E to <unk> and <unk> / C , finishing with G , <unk> then <unk> , before resolving back to C. The 8 @-@ bar choruses progress from F to G to C , then <unk> and E before ending on <unk> , a C chord substituted for <unk> in the final bar . The 4 @-@ bar <unk> begins with F , then G , before resolving on C. With a duration of 3 minutes and 3 seconds and a time signature of 4 / 4 , the song 's tempo falls around 75 beats per minute . 
