Thanks for telling, John. I knew this possibility existed but didn't know how to do it.
I then tried several ways to exclude both BS and NotMusic (by some posters written 'not music') at the same time. It seems to be impossible, but I could do it in a two step process, first excluding BS and then excluding Notmusic on the resulting threads.
It would help me a lot on my days with only a little time if the posters would use the label 'BS' consistently and not invent their own labels.

Wolfgang