Though REM songs are credited to the whole band, I do find it interesting to learn where the origins for each came from.
Airportman - ?
Lotus - Buck
Suspicion - ?
Hope - ?
At My Most Beautiful - Mills
The Apologist - ?
Sad Professor - Mills
You’re In The Air - Buck
Walk Unafraid - Buck
Why Not Smile - Mills
Daysleeper - Buck
Diminished - Buck
Parakeet - ?
Falls to Climb - Buck
I’d always guessed Parakeet was Mills but I don’t really know how to back that up.
Airportman & Parakeet are Mike’s and I’m fairly sure that The Apologist is Pete. as for the other 2 - 
If I’m guessing - Suspicion -Peter, Hope - Mike but it’s just a guess…
I would guess that Hope was Peter Buck. There was a lot of talk about how they’d used old 70s synthesisers and drum machines that he had. Chord progression-wise, it sounds Buck-ish.
But I could be wrong!
Agreed…it seems like Buck tended to delve into experimental instrumentation around then. Hope could be him, and I wonder about Airportman as well. Suspicion also seems up his alley.
Parakeet could certainly be Mills, especially when peeling away the electronica.
I’m going to commit the terrible sin of asking now, looking after, but also: do we have similar sorts of lists or guesstimates for other albums? I’m always really curious about this sort of thing but can never quite pin down a few songs in their catalog.
edit: lol, indeed, I just now noticed the Automatic one! Oops! 
I don’t know if it was a rumor or not, but I heard that Michael wrote some of the synths on Airportman. Anyone know?
If I heard his Rubin interview correctly, he didn’t start messing around with synths until he started his solo career.
He did play guitar a couple of times on Up, and I think was involved with some random sound effects (such as the bridge in Uberlin), and humming some arrangements (like the horns on Imitation of Life).
That’s cool. I’d rather know for sure.
Michael played keyboards in Tanzplagen way back in the early 80s.
He sure did, but he also played in quite a few REM songs - Stand, Endgame, Fireplace… I don’t think that there’s an album in their canon in which he didn’t played on… maybe Accelerate
What did he play on those songs? He’s listed as melodica on Endgame, but I’m not aware of there being a synth?
He played all kind of stuff but mostly keys. piano on Fireplace, organ on Stand, some keys on Everybody Hurts and on How the West Was Won… It Crawled From the South mentions some other early numbers he playes on, I’ll try and scroll through it when i’ll have a chance
Did he play organ on Stand, or did he do the single piano notes (a la Fireplace)? I thought the organ on Everybody Hurts was Mills (I recollect him talking about getting a compliment from John Paul Jones)?
Organ on Stand accrding to It Crawled From the South.
and the John Paul Jones compliment for Mike was regarding his bacground vox on try Not to Breath, Everybody Hurts’s working title is Michael’s Organ for a good reason
Great book, It Crawled From the South. I’ll have to dig that out again. The definitive R.E.M. biography.
Why would John Paul Jones be discussing Try Not to Breathe? He didn’t work on that song. I recollect Mills commenting on how Jones complimented him on the organ part later in the song and how he tied it in with his bass line.
you are correct, drivernate. it was “everybody hurts” where JPJ complimented mills on an organ flair
He may have complimented him more than once (I remember Mike saying that JPJ said that the backing vox on Try Not to Breathe reminds him of John Lennon) but anyway- Mike is the main keyboard player on Everybody Hurts, Michael’s parts are usually quite insignificant and buried in the mix
Found the quote from It Crawled From the South:
There's definitely a nod to the Rolling Stones on "Everybody Hurts",' Mike told Guitar magazine in 1993.The
ascending bit is very similar to the ascending boys’ choir on
“You Can’t Always Get What You Want”.’ Mike was particularly
excited about meeting John Paul Jones, who made his day by
complementing him on one of his more subtle embellishments to
this track. In the last verse, the harmony is carried by organ
instead of piano. `Just coming out of the verse, I kick in the
Leslie [the Hammond organ’s revolving speaker phasing effect]
and it starts to spin, and then I turn it off. You barely notice
it. And John sidles up to me and goes, “Nice touch on the
Leslie, there.” And I was like, “Whoa! Thank you! Yes!” It just
made my week.’