I have just seen that there is a free tour behind the scenes of the Tonhalle (Zurich's concert hall) on November 1, at 6.15 p.m. If you don't have a ticket for the concert afterwards, you have to deposit CHF 20 for the tour, but you get that back.

These tours behind the scenes take place on a regular basis. I will post it as an event when I go there, myself. This time, I can't. I assume it will be in German, but then, if we go as a group, I can translate.

Idgie