MacDonald characterises McCartney's "When I'm Sixty-Four" as a song "aimed chiefly at parents", borrowing heavily from the English music hall style of George Formby, while invoking images of the illustrator Donald McGill's seaside postcards. Its sparse arrangement includes clarinets, chimes and piano. Moore views the song as a synthesis of ragtime and pop, adding that its position following "Within You Without You" – a blend of Indian classical music and pop – demonstrates the diversity of the album's material. He says the music hall atmosphere is reinforced by McCartney's vocal delivery and the recording's use of chromaticism, a harmonic pattern that can be traced to Scott Joplin's "The Ragtime Dance" and "The Blue Danube" by Johann Strauss. Varispeeding was used on the track, raising its pitch by a semitone in an attempt to make McCartney sound younger. Everett comments that the lyric's protagonist is sometimes associated with the Lonely Hearts Club Band, but in his opinion the song is thematically unconnected to the others on the album.