Tragically, immediately following this recording every single one of these people was crushed as Evangelion units 01 and 02 descended through the ceiling on their way into Terminal Dogma.
Given the way sound travels, is it really possible to get that large of an auditorium to sing on time, or did they have a lot of monitors around to keep em together?
I'm almost certain there would have to be monitors. I sang this with a 140 member choir last year, and can't imagine everyone staying together otherwise.