"Mercy, Mercy, Mercy has been re-recorded numerous times, most notably by The Buckinghams, who reached # 5 in August 1967, adding lyrics to the tune. Musicians on the Buckingham's version included James Henderson, Lew McCreary and Richard Leith on trombone, Bill Peterson, Bud Childers on trumpet, John Johnson on sax, Lincoln Mayorga on Wurlitzer electric piano, Dennis Budimir on guitar, Carol Kaye on bass, and John Guerin on drums.
The tune is in the key of B-flat major and has a 20-bar structure with four distinct sections. The chord progression is mainly made of dominant-seventh chords on the first, fourth and fifth degrees, giving the song a bluesy feeling although it does not follow a typical blues progression. The subdominant (IV) chord in the beginning section emphasizes this bluesy feeling. In the second section, the tonic chord alternates with a second-inversion subdominant chord, creating a parallel to the I-IV-V progression (in which the tonic moves to the subdominant).