First thing that came to mind is Ian Gillan's G5 "WHHHYYYYYYYYYYY should I die?!" in Gethsemane, from Jesus Christ Superstar (1970). Come to think of it, that whole album has a few: Pilate's "then I heard them mentioning my name, and leaving me the blame" and Judas's "I shall be dragged through the slime and the, slime and the, SLIME AND THE MUD!"
Watching this performance of Ted Neeley as well (at age 63!). Apologies as I have posted this video before. I have no idea what goes on backstage during musicals, but do performers often watch their fellow actors on stage, and be so moved by a song like these guys and gals are?
https://youtu.be/0rEVwwB3Iw0?t=183
I remember quite well your original post of this.
Along with this, add 'alright.... I-I-I-I-I-I 'LL DIE'.
And the foreboding guitar and the first notes of 'Overture'.
Speaking of which, I'll also add Dream Theater's 'Overture 1928', along with many moments during 'The Razor's Edge' Score version.
Two 'Pavlovian' leading up to those chills: the ending of the 'Sgt. Pepper reprise' as it fades into those first few guitar notes of 'A Day In The Life'. There's about twenty more during the song.
'Good Company' from 'A Night At The Opera': I enjoy the dixieland ending instrumental, but the goosebumps start at the reprise of the intro, hit overdrive on that lovely short piccolo......
.......and then, of course, go off the charts at ...... 'Is this the real life, is this just fantasy.......'