Sally' and say it sounds so easy to write. But it's the most difficult thing we've attempted. Writing a three-chord song that's clever is not easy". In his authorised biography, Many Years From Now, McCartney remembers "I'm Down" as entirely his composition, but raises the possibility that Lennon added a few lyrics or made minor suggestions in the writing process. In a 1972 interview, Lennon credits the song to only McCartney, but in his 1980 Playboy interview he instead suggests he provided "a little help". Musicologist Walter Everett argues that McCartney often forgetting the song's lyrics in concerts suggests he wrote the song quickly and with little practice. "I'm Down" is in the key of G major and is in 4/4 (common time). A simple twelve-bar blues number extended into fourteen-bars, the song uses only the chords I, IV and V. One of the few Beatles songs to feature a simple verse form, musicologist Alan W. Pollack suggests that, in the context of the Beatles' 1965 compositions, its simple format is stylistically regressive. The song opens with a solo vocal from McCartney, which music critic Tim Riley sees as the part of the song bearing the most resemblance to "Long Tall Sally", with "one mad voice screaming at the top of its lungs". With neither bass nor drums to clarify the key or downbeat, Pollack writes that "no matter how many times you've heard the song", McCartney's opening vocal is "an effect which retains the power to startle". The repeating refrains incorporate improvisational scat singing and, according to Pollack, get "successively wilder and less structured" with each repeating. Everett writes the concluding coda serves the purpose of "[raising] the rock-and-roll spirit to a higher level of excitement than does the song proper". The song's lyrics tell the story from the perspective of a pained lover who is frustrated due to an unrequited love. Rather than a lament, the music functions as a "celebratory frenzy" of self assuredness. Pollack writes the song's style originates in a 1950s R&B cliché, being "a semi-improvisatory rave-up" where the lyrics are unimportant compared to the tone in which they are sung. Riley describes the song as an instance of "dancing on your problems", as heard in rock and roll oldies like "That's All Right" and "Blue Suede Shoes". Author Ian MacDonald suggests that, besides being a blues send-up, the lyrics are "a tongue-in-cheek response to