"I Feel Fine" is a song written by John Lennon (credited to Lennon–McCartney) and released in 1964 by the Beatles as the A-side of their eighth British single. The song has one of the first uses of guitar feedback in popular music.

Lennon wrote the guitar riff while in the studio recording "Eight Days a Week". "I wrote 'I Feel Fine' around that riff going on in the background", he recalled. "I told them I'd write a song specially for the riff. So they said, 'Yes. You go away and do that', knowing that we'd almost finished the album Beatles for Sale. Anyway, going into the studio one morning, I said to Ringo, 'I've written this song but it's lousy'. But we tried it, complete with riff, and it sounded like an A-side, so we decided to release it just like that." Both John Lennon and George Harrison said that the riff was influenced by a riff in "Watch Your Step", a 1961 release written and performed by Bobby Parker and covered by the Beatles in concerts during 1961 and 1962.Paul McCartney said the drums on "I Feel Fine" were inspired by Ray Charles's "What'd I Say".

At the time of the song's recording, the Beatles, having mastered the studio basics, had begun to explore new sources of inspiration in noises previously eliminated as mistakes (such as electronic goofs, twisted tapes, and talkback). "I Feel Fine" marks one of the earliest examples of the use of feedback as a recording effect in popular music. Artists such as the Kinks and the Who had already used feedback live, but Lennon remained proud of the fact that the Beatles were perhaps the first group to deliberately put it on vinyl.

"I Feel Fine" is written in 4/4 time with drummer Ringo Starr's R&B-influenced beat (based on the "Latin" drumming in Ray Charles's hit "What'd I Say") featured through most of the song except for the bridge, which has a more conventional backbeat. After a brief note of heavy feedback (see below), the intro begins with a distinctive arpeggiated riff which starts in D major before quickly progressing to C major and then G major, at which point the vocals begin in G. The melody, unusually, uses a major third and a minor seventh, and has been classified as Mixolydian mode. Just before the coda, Lennon's intro riff (or ostinato), is repeated with a bright sound by George Harrison on electric guitar (a Gretsch Tennessean). The song ends with a fadeout of the G major portion of the opening riff repeated several times.

...
Wikipedia