I previously mentioned the street theatre in Cambridge (here). Here is a performance on the street in Munich.These musicians are from Mongolia, and the singing they produce is quite extraodinary: a very low-pitched buzzing sound. I have no idea how it is made.
I have seen these singers on the Discovery Channel (or somewhere like that); but to see them actually performing is quite special. And to come across it in a pedestrian precinct in the middle of Munich is rather unexpected.