This song is about taking acid. John Lennon appropriated much of the wording from the The Psychedelic Experience: A Manual Based on the Tibetan Book of the Dead, a counterculture page turner by Timothy Leary, Richard Alpert, and Ralph Metzner. Their book helpfully adapted the Tibetan Book of the Dead for a new hypermodern chemical intoxication experience. The song's original title was "The Void." The droning that permeates the song is a tamboura, traditionally used in Indian modal drone. The vocal effect is an attempt to imitate the famous overtone throat singing of Tibetan monks.
Simplistically, the theme of the song is the ideal of "ego death" that both Buddhists and LSD practitioners seek via different methods. At this point of his stratospheric fame, John Lennon also began seeking ways to pare down the expectations and pressure that came with his notoriety. "Ego death" was all too attractive to someone for whom ego had already made its maximum impact.
It's the final song on the Beatles' 1966 album Revolver. Revolver was the peak of the Beatles as tinkering songsmiths, a collection of short, brilliantly efficient recordings, almost all well under three minutes in duration. There was no overriding concept connecting the songs like their next album Sgt. Peppers would have, no indulgent expansion of song structures and run times as became more common.
Each song was its own mini-concept, its own prototype. Each song was a new lesson in musical ambition. And yet none of the rest compare to the revolutionary impact of "Tomorrow Never Knows." John Lennon had a knack for developing one special song per album that looked forward to the next frontier.
"Tomorrow Never Knows" pulled out all the stops, pairing a simple chord structure (a single droning chord with short two-chord interludes) with boundary-smashing instrumentation and tape effects. It cooks at a great pace, with an underrated heavy Ringo drum part. On the album, the run time is less than three minutes, but I see the potential of improvisation to extend it far longer. It's a trance of a song for a performer.
The song ends on the line "the end of the beginning." Lennon's talking about the possibility of life after death, with life being only the beginning. And yet, positioning this as the last song of the last traditional Beatles album, he is also predicting the end of one stage of the Beatles' career, with this very song portending the advanced concepts yet in store.
Besides taking the Beatles new places, the song became a model for many later drum and bass masterpieces. In the '90s alone, both Beck's "New Pollution" and the Chemical Brothers' "Let Forever Be" are confident re-imaginings. It is now a genre unto itself.
Link: https://genius.com/The-beatles-tomorrow-never-knows-lyrics