Mariachi bands may or may not be allowed on the tram

The powers that be recently got together and decided that the signs inside Zurich public transportation were unacceptably lacking in humor, stereotypes, and surrealism. Much to my delight, they fixed all three problems at once, making my daily tram rides a lot more entertaining.
Care to guess what the following diagrams are trying to tell us?
Before you go out and buy a sombrero and a hand saw to bring on your next trip to Zurich, It may help if I explain that in the German-speaking world, a red circle around something means “no”. Yes, it would be clearer if they went a step further and put the slash that the rest of the world understands to mean something is forbidden, but then it wouldn’t be nearly as fun to guess at the meanings of these things.
PS – People look at you funny when you take pictures of signs on a crowded tram.
[See updates to this story under the tag mariachis.]
