don't really get this...maybe I'll read the book to catch up!
Here's what I think is the explanation (with maybe some details here and there wrong): Radio Ballet was a form of protest, or a kind of social statement. Basically, the train stations in Germany had (or have, not sure if it's all still in effect) laws saying that you can't loiter, with security cameras everywhere to catch you if you're breaking the law and acting suspicious in any way. Radio Ballet was a pirate radio performance that instructed people to do things that technically broke the law, but, since everybody (about 400 people total) was dispersed, there was no way the train station could enforce the law. I don't think the book has a ton of information on it, but it explained the basics and what caught my eye was a still of a video of someone participating in Radio Ballet.