In the Anthology documentary, McCartney said the famous introduction to ”I Feel Fine” was accidental when Lennon placed his guitar against the wall too close to his amplifier.
Another version by producer George Martin is that John always had the volume knob up high and he understood that he could exploit this. Thus the feedback was intentional.
“George and I play the same bit on the guitar together- that’s the bit that’ll set your feet- a-tapping, as the reviews say…..I defy anybody to find a record- unless it’s some old blues record in 1922- that uses feedback that way. I claim it for the Beatles.”
The song was a mix of mainstream and avant-garde- spirit and energy that resulted in something truly unique. It remains to this day one of the most joyous and completely unpretentious celebrations of love in the history of pop music.
“I Feel Fine” is a good example of The Beatles’ drawing on a rhythm and blues tradition while at the same time adding their own unique unexpected contrasts and unusual subtleties of melodic detail. Instead of using “ooh”s as in previous songs, they had already begun to seek other means of expressing excitement, involving mental and vocal techniques.
Paul and George’s high harmony in the refrain when they sing I’m in love with her and I feel fine is the highlight of the song. Another is Ringo’s drumming which can only be defined as “soul-jazz” like a “Latin R&B shuffle.”
He would later comment:
“When I’d do a fill I always felt I went into a blackout. I didn’t know what I’d do.”
“I Feel Fine” is about how the speaker has a very loving relationship with a woman that makes them both happy. He is also proud that he has enough disposable income and generosity to give his girlfriend jewelry.
However, the statement that he gives her plural "rings", as opposed to one special diamond ring, suggests that he simply buys her diamonds to win her over rather than as a sign of commitment. It’s implied or insinuated that the reason this woman "loves" the author so much and is so "good to" him is that he buys her material things.
He does seem so happy and so unaware, but you see little hints slipping through. He's going by her say-so in the relationship and being lead about by the heartstrings, but really he's just being used. There is a much darker tone to the composition than it would initially appear.