We were out with our German neighbors the other night and the topic of Germany's numerous rules came up. Our neighbor mentioned that the musicians in the subway need to get special permission to play. I never really gave much thought to the musicians we have along the entryway to our metro station although it's always fun to guess what we'll get today--accordian, flute, or violin. I'm still waiting for some bongos to show up though. :-)
Apparently, there is a regulatory office that authorizes the street musicians and performers in the tourist areas to do their work. They only give out something like 20 permits a day and every day a performer wants to perform, they have to go to this government office for the permit. They play for a government official and if they're deemed good enough and there are still permits left for that day, they are allowed to play. But just for that day. The next day, they have to apply again. If they do get a permit, they are supposed to display it for all to see.
In any case, I love walking down the tunnel lined with bikes (even now!) with music enveloping you, welcoming you into the shelter of the station's entryway.