
Hi, Reiko
Welcome to Zurich!
Great - the more the merrier. No worries - this is a low price concert in a church. I expect that the artists and some very few others will be in full gear and many people in the crowd will be in smart casual, but the majority will be just tidy but casual. Even in the opera, you will always have some people in (clean, of course) jeans and t shirts, and no one frowns at them. I would recommend taking a long sleeved shirt or a jacket along, though, as it can be a little colder in the church than outside.
By the way, the seats are not numbered, so that we can all go and sit together, even if someone should decide to get a ticket in advance. I have bougt some additional tickets when I bought mine, already, and they still had enough (as I said the church is bigger than one would think when seeing it from the outside), so not to worry about that.
Looking forward to meeting you
Idgie