‘#9 Dream’ is the second single off of John Lennon’s 1974 album Walls and Bridges. Like Paul McCartney’s ‘Yesterday’, the song’s melody and memorable chorus came to Lennon in a dream. The ‘9’ in the song’s title is a reference to Lennon’s lucky number.

At the time of recording, Lennon was on his infamous ‘Lost Weekend’–an 18-month period spanning 1973 through 1975 in which he was separated from his wife Yoko Ono. Over the course of this period, Lennon reconnected with several old friends (including Paul McCartney) and his identity as an ex-Beatle, which proved to be creatively reenergizing.

Given the nostalgic themes of the song, many have speculated that Lennon is in fact dreaming about his time in the Beatles, but the mysterious nature of the song is better left that way.