The song has one lyric, its title, and continues chanting the words through an increasingly chaotic set of sounds.
McCartney once described it as “lounge-style music,” reminiscent of listening to an artist in a smokey underground bar.
John Lennon spoke about how he first came up with the idea long before he began recording it.
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“I was waiting for him in his house, and I saw the phone book was on the piano with you know the name, look up the number. That was like a logo, and I just changed it.
“It was going to be a Four Tops kind of song – the chord changes are like that – but it never developed, and we made a joke of it.”
In a final reveal, he added: “Brian Jones is playing saxophone on it.”
The guitarist’s inclusion on The Beatles track is one of the final songs released with his credit on.
Before Jones’ legendary addition to the song, McCartney revealed Lennon brought You Know My Name (Look Up The Number) to him at 15-minutes long.
He said: “It was John’s original idea, and that was the complete lyric.”
“He said: ‘It’s just like a mantra.’ So we said, ‘Okay, let’s just do it.’”
He later added: “We did it over a period of maybe two or three years. We started off and we just did 20 minutes and it didn’t work.
“Then we tried it again, and we had these endless, crazy fun sessions … And it was just so hilarious to put that record together.”