I heard it was Bill but it kinda sounds like it might be Mike or just Michael doing an overdub which would make sense cause they never do that part live. I have a similar question on who sung the response parts in Sidewinder as well
Chronic Town (1982)
Wolves, Lower: Harmony with Mike on the "House in order." Backing vocals on the chorus.
Carnival Of Sorts (Boxcars): Harmonies with Michael on "gentlemen, gentlemen" and "are pulling" with Mike.
Gardening At Night: Harmony on the chorus.
1,000,000 (Live): Harmony on the chorus.
Murmur (1983)
Radio Free Europe: "Calling out" backing vocals with Mike on chorus. (maybe just live not sure about studio)
Pilgrimage: Harmony on "Take a turn." And the "Ahahh." Backing vocals on the chorus, lower vocalizations on the bridge while Mike does the higher ones.
Laughing: Harmony with Michael on chorus.
Talk About The Passion: Backing vocalizing on the chorus, he does it live but I don't hear it in studio.
Moral Kiosk: Harmony vocalizing with Mike on chorus, backing vocalizing during the bridge.
Perfect Circle (Live): "ooos" with Mike on the last few choruses.
Catapult: I think it's either him or Stipe backing himself up who repeats the title in the chorus.
Sitting Still: really beautiful "ahhs" with Mike on the chorus.
9-9: Harmony with Michael in the chorus.
West Of The Fields: Harmony with Stipe and Mills on the chorus, in the bridge he does a "hey ahh" kind of sound, it's easier to hear live.
Reckoning (1984)
Harborcoat: Backing vocals on chorus: "Harborcoat is long on me/away, Harborcoat is gone, woah woah woah woah."
Second Guessing: Vocalization in the pre-chorus.
Letter Never Sent: He does the first "Heaven is yours" in the chorus before Stipe comes in to harmonize with him.
(Don't Go Back To) Rockville: Harmony with Stipe and Mills in the chorus
Fables Of The Reconstruction (1985)
Maps And Legends: Singing the title with Mike in the chorus.
Life And How To Live It: Backing vocalizing with Mike in the chorus.
Old Man Kensey: Vocalizing with Mike in the bridge.
Can't Get There From Here: Harmony backing vocals with Mike on the chorus, vocalizing on the bridge.
Green Grow The Rushes: "Green grow the Rushes grow" with Mike near the end.
Wendell Gee: high Harmony near the end.
Life's Rich Pageant (1986)
These Days: He says one of the "Threes" in the second verse, not singing but technically a vocal.
Fall On Me: he repeats "It's gonna fall" at the start of every stanza of the chorus, you can hear him faintly in the first two choruses, but it's clearer in the last section, he also does a vocalization in the bridge whilst Mills is leading. This is probably his most well known part.
The Flowers Of Guatemala (Live): I think he does the "Oh-oh-oh" part in the chorus that was done by Michael in studio, I'm not sure though.
I Believe: Harmony with Michael on the "on your honor" line in the second and third verse.
What If We Give It Away?: Harmony with Michael on the bridge.
Document (1987)
It's The End Of The World As We Know It: I heard he does the "Time I had some time alone" part but I'm not sure, they never seem to do that part live. But he usually sings along with Stipe and Mills in the chorus in live performances. (ie unplugged)
The One I Love: Low in the mix vocalization in the chorus, he does it when Mike starts singing, he also might be repeating the word "love" after Michael in the verses.
Green (1988)
Get Up: Response to Stipe in the chorus: "Dreams, they complement my life."
You Are The Everything: "Say, say, the light" backing vocals with Mike.
Stand: Harmony with Mike on "Now face West/North." In the chorus.
Orange Crush: Harmony with Mike on the verse backing vocals.
I Remember California: "The edge of the continent" falsetto backing vocals near the end, better heard live.
Out Of Time (1991)
Radio Song: He sings the second verse on one of the demos.
Near Wild Heaven: The falsetto vocalizations in the chorus.
Shiny Happy People:"Dit dit dit." near the end.
Belong: singing along with Stipe and Mills throughout the song, he does the high falsetto.
Country Feedback: The first and last two "It's crazy what you could've had." Maybe, I don't know for sure.
Automatic For The People (1992)
Try Not To Breathe: Backing vocals on the chorus: "I have seen things you will never see" with the radio like effect.
The Sidewinder Sleeps Tonite: He might be repeating Stipe in the chorus or it could be Mills or Stipe backing himself up.
Monty Got A Raw Deal: "Waste your breath" backing vocals with Mike on the chorus.
Ignoreland: "Yeah, Yeah, Yeah!" With Mike in the chorus I believe.
Man On The Moon: Backing vocals during the last few choruses: "Oh ah ah oh ah ah oh." he might also do the "ooos" in the verses or it could be Mills or both.
Find The River: The lower vocalizations in the chorus while Mills does the higher ones.
Monster (1994)
Crush With Eyeliner: Falsetto vocalizations in the chorus with Mike.
Bang And Blame (Live): Harmony on the chorus.
Tongue: Falsetto harmonies with Mike around the chorus area, you can see him do it in the music video too.
New Adventures In Hi-Fi (1996)
Binky The Doormat: "Yeah, Yeah, Yeahhh" backing vocals near the end, very faint.
Dead Letter Office (1987)
There She Goes Again: "There she goes" backing vocals with Mike throughout the song.
Pale Blue Eyes (Live): Harmony on the chorus with the Mikes.
Femme Fatale: Repeating the title with Mike near the end.
B-Sides, Rarities, And Covers:
He gets his own verse on the I walked with a zombie cover and Spooky which he messes up some lyrics.
Fretless (live): Substitutes Kate Piersons "Don't talk to me" backing vocals in the chorus with Mike.
Funtime: Backing vocals with Mike.
The Lion Sleeps Tonight: Very likely that he does the bass vocals but not 100% sure.
Arms Of Love: "Into the arms" backing vocals with Mike.
Wicked Game: "This world is only gonna break your heart" backing vocals with Mike.
Wall Of Death: He sings "My chances" near the end of the song.
He sings lead on his solo singles: my Bible is the latest TV guide and the cover of the new colony six song Things I'd like to say.
If there are any I missed lmk please
Matt Holt is my favorite metal vocalist and unfortunately I never see anyone really analyzing his style. From what I know he sung a bit nasally, he sounded like he had a cold when singing but still sounded phenomenal, the screams might be a mix of false chord and fry.
I've been singing for a while but still have a long way to go, I haven't found my mixed voice or learned a good screaming technique.
You can see this warehouse looking building while you're riding the gondola but you never go here, cut Content maybe?