Silent discos as multithreaded and noiseless outdoor concerts
The New York Times has an interesting article, "Silent Discos Let You Dance to Your Own Beat," about outdoor concerts that are noiseless--because the music is delivered by headphones--and multi-threaded, in that people can choose to listen to different music streams delivered by different djs all playing simultaneously.
This is interesting on many levels. It's one way to provide outdoor music "festivals" in places that are adjacent to residential areas...
Also see "Silent disco at BBC6 Fringe Festival, from the Victoria Warehouse (Manchester, UK) website.
Quietclubbing is an organization in New York City that sponsors events at different types of places--parks, beer gardens, etc.--and venues across the city