Singing in such a choir you get to attend more than your fair share of weddings and funerals, and even though you mostly don't know the happy couple or the deceased person (delete as applicable) they are usually emotional occasions so that's when, despite it being a choir of amateurs (in the true sense of that word), the professionalism kicks in and emotions are put to one side in order to get the job done. That job of course being to be a part of the team (clergy, servers, organist, conductor, choir, etc) who make the event happen and facilitate whatever spirituality or other feelings the people in the congregation are having. Whether the individual choir members feel that spirituality too is secondary, but discussion of that is for another time.
Much is made of the fact we sometimes sing on the radio ('Scotland's most broadcast choir' is the phrase regularly bandied around) but that stuff's just icing, today is the real thing.
Today will be difficult, but it will be done because Alistair was not only our friend, but he was one of us, and it'll be done because it's our job.