In the 90s I knew a guy in high school who walked around the school in a black trenchcoat with portable speakers tucked inside that were continuously playing Western movie themes. I can only imagine how that bit of creativity would go over these days.

Sometimes, but not too often, in Berlin of all places you encounter someone biking around with a massive speaker attached to their bike blaring (obviously) techno

Not always a bike. Sometimes just a trolley or a handcart or a custom jerry-rigged contraption.