According to the Zombie Heaven liner notes, fifty years ago to-day (12 June 1967), the Zombies did some work on Odessey and Oracle. The entry for 12 June reads: "EMI Abbey Road Room 53 recording: 'Friends of Mine', 'A Rose for Emily', 'This Will Be Our Year' (mono mixing)."
It seems that this was the mixing session for the mono versions of these songs; however, "A Rose for Emily" is mentioned again later in the list of production dates. 10 July lists "recording... 'A Rose for Emily' (reduction master)," and an-other mono mixing session with "A Rose for Emily" was on 20 July.
According to the Zombie Heaven liner notes, the cello part "was included in some initial mixes but eventually discarded." So it seems that this 12 June mixing session was for the version with cello.
"Hung up on a Dream" was the other song recorded at that 10 July session, and because that includes mellotron, I'm assuming that 10 July was also when the mellotron part for "A Rose for Emily" was recorded (which was also later discarded).
