This version sounds different from the one in the film. The introduction section is missing and some instruments from the orchestra are also missing. It may be a different recording or cut from the tape to fit on the record.
The choir can be heard in a few sections throughout the film but was never credited for their appearance in the film score from what I can find. There is another song in the film sung by the choir that was never released on a record https://www.youtube.com/watch?v=uPro3_GnOfM&t=6151s (1:42:31)