The title came from an expression Ringo Starr used. They chose it to take the edge off the heavy philosophical lyrics. Working titles for the song before Ringo gave them inspiration were "Mark I" and "The Void."
John Lennon wrote this, and described it as "my first psychedelic song." It was inspired by Timothy Leary and Richard Alpert's book The Psychedelic Experience, which Lennon would read while tripping on LSD. Lennon recorded himself reading from the Tibetan Book of the Dead, played it back while tripping on LSD, and wrote the song.
Each Beatle created strange sounds which were mixed in throughout the recording, often backward and in different speeds. McCartney had the idea for using tape loops to create effects.
This used 16 tape loops. Several people remember standing around the room holding pencils for the tape to loop around and back into the recording machine as the various sound effects and instrumentation were faded in and out.
The vocals were forced through a Leslie (revolving) speaker. Lennon desired the effect that the listener could hear the words but not hear him, like a group of Tibetan monks chanting on a mountain top.
John Lennon used only one chord in this whole song, which creates a hypnotic feeling. For his vocals, he asked producer George Martin to make him sound like the Dali Lama.
This was the first track recorded for the album yet the last on record.
There are 2 guitar solos on this song - both were heavily processed.
On May 6, 2012, this song was featured in an episode of the popular American TV show Mad Men. The episode was set in 1966, and part of the plot was the ad agency in the show helping a client capitalize on Beatlemania. This was a big deal, since Beatles songs are very rarely licensed for TV shows - at least in their original versions. Cover versions and performances (think American Idol) show up from time to time, since those just have to be approved by Sony/ATV, which owns the publishing rights. Getting permission to use an actual Beatles recording requires permission from Apple Corp, which is controlled by The Beatles and their heirs.
The Wall Street Journal reported the payment for the song at $250,000, and Mad Men creator Matthew Weiner had to reveal to Apple exactly how the song would be used, which was a big deal since he is very secretive about scripts. In the episode, the main character Don Draper has trouble adapting to changing musical times. He plays this song to see what all the fuss is about, and after character-developing montage while the song is playing, he switches it off. The song then comes back to play over the closing credits.
Phil Collins covered this on his debut solo album. Like The Beatles did on Revolver, Collins used it to close the album. (thanks, Adrian - Wilmington, DE)
Our Lady Peace remade this song for the soundtrack to the movie The Craft. It's played during the opening credits. (thanks, Patrick - Bremen, GA)
Oasis gives a tribute to this in their song "Morning Glory" with the line "Walking to the sound of my favorite tune Tomorrow Never Knows what it doesn't know too soon." Oasis is well know for their similarity to the Beatles. (thanks, Dominic - Pittsburgh, PA)
This song is featured on the 2006 Beatles album Love
(a soundtrack to the Cirque du Soleil show based on their music) remixed with "Within You Without You
." (thanks, Ryan - London, England)