Tomorrow Never Knows
Rumor has it that McCartney's "Tomorrow Never Knows" guitar parts are actually transplants from "Taxman."
Titled simply "Mark 1" at the time recording commenced on April 6, 1966, the song was the product of Lennon's experience with LSD, which he'd taken the previous January. Using lines from The Psychedelic Experience, an LSD manual based on the Tibetan Book of the Dead, he wrote the song as a mantra composed of one repeating melody line over driving bass and drum track.
"It's only got the one chord, and the whole thing is meant to be like a drone," Lennon told Martin and EMI engineer Geoff Emerick. Additionally, he explained, he wanted his voice to sound "like the Dalai Lama chanting from a mountaintop."
Says Emerick, "I was thinking, Well, I've got an echo chamber and ... that's all! I didn't know what I was going to do. And suddenly, there it was, staring me in the face!" "It'' was the studio's Leslie rotary speaker cabinet, a standard piece of equipment for organs but one that had never been used for any other instrument or for voice. As Lennon's voice came swirling through the Leslie, the assembled group listened in awe from the control room. "It's the Dalai Lennon!" exclaimed McCartney.
https://www.guitarworld.com/artists/watch-beatles-dissect-tomorrow-never-knows