Reviewed by Ian MacDonald, in Revolution in the Head:

McCartney's most rhythmically unorthodox song, MARTHA MY DEAR was recorded ten days after a period of intense rehearsal work on Lennon's similarly irregular HAPPINESS IS A WARM GUN. Since, like HAPPINESS, it includes an ascending bass phrase which temporarily expands the metre (fourth bar: 6/4), it's possible that McCartney, his musical funnybone tickled by his partner's eccentricities, here set out to create something equally tricky for his own amusement. As brilliantly fluent as Lennon's song is dark and crabbed, MARTHA MY DEAR is the most exuberant expression of its composer's jaunty personality since PENNY LANE. Yet, while PENNY LANE has a point of view, MARTHA MY DEAR is a part-technical jeu d'esprit with a confused lyric in which its author's Old English sheepdog somehow gets muddled up ina recent love affair. Scintillatingly gifted as this song is, it's also virtually devoid of meaning.

The key of E flat major suggested a brass band and George Martin swiftly assembled one, the bulk of the recording being accomplished in a single brisk day's work. None of the other Beatles appears to have been involved - a tribute to McCartney's facile versatility and a measure, perhaps, of his colleagues' indifference to this breezy song.