McCartney Times

The Beatles and producer George Martin assembled at Abbey Road’s Studio Two on April 6, 1966, their first recording session together since they’d wrapped the Rubber Soul LP almost five months before. They would begin work on Revolver by recording “Tomorrow Never Knows,” the song that would close out the album.The lyrics were primarily written by John Lennon, who borrowed from The Psychedelic Experience, a book written by LSD proponents Timothy Leary and Richard Alpert. The book was an adaptation of the centuries-old Tibetan Book of the Dead. Leary’s introduction to the book reads, “Whenever in doubt, turn off your mind, relax, float downstream.” That would become the song’s first line.

Source: 50 Years Ago: The Beatles Kick Off ‘Revolver’ Sessions With ‘Tomorrow Never Knows’