Recorded in June 1964, Lennon said "I Should Have Known Better was just a song: ”It doesn’t mean a damn thing.”
Composed by Lennon, at first he hammers the melody on the same note. The Italian composer Monteverdi discovered the effect of hammering on the same note. He called the style "stile concitato".
Then comes the middle part which has a change of keynote, which is unusual with such a change in a middle part. And then the rise in falsetto. Typical of Lennon's songs, there is also a rise of excitement. When you think that the mood will cool a little - when you come to the middle part - the excitement instead increases.
Says musicologist Tim Riley:
“John and Paul’s vocal harmony is patterened after the Everly Brothers- minus the refinement. The spirit in the harmony and the expectatnt silence that follows heightens the sense of anticipation, a different take on the same Everly’s effect before the “ooh-la-la” in “Wake Up Little Suzie.”
With its driving harmonica introduction and John’s acoustic guitar engaged in a rhythmic duet with Harrison’s emphatic Rickenbacker accents, the song can’t help but warm even the most cynical of hearts.
Author Jonathan Gould defines the track as:
“A supercharged version of “Love Me Do,” complete with a coy lyric, a wailing harmonica, and a double-tracked vocal from John on which he asserts his presence by sustaining the pronoune “I” for six full beats at the start of every verse. Paul’s subtle bass line and George’s brief, albeit well structured twelve-string guitar solo, are carefully strung together."
In the middle eight, each line ends with a differently intoned exclamation ('oh-1', 'oh-2', and, the 'uh-huh-huh!' falsetto with its orgasmic effect), it's the way the lines themselves are structured - so disconnected and unpredictable upon first sight, and then so logically "sewn" together with the '...you're gonna say you love me too...' conclusion.
George’s chiming on the Country Gent announces the exotic chord changes that are continuously re-articulated by Lennon’s Gibson—an excellent example of the album’s stratification of guitar timbres. In the bridge, George plays half time (instead of double time) against the unaltered rhythmic pattern in the rest of the band, suspending chords as the others play through them.
This is the first recorded song on which George Harrison plays the 1963 Rickenbacker 360 12 guitar, the very first electric twelve-string guitar. It’s use here would make it instantly popular among members of the burgeoning "folk-rock" movement. The Byrds' Roger McGuinn is said to have gotten the idea for the genre after hearing this song.