This summer on the corner of Pioneer Square in Portland I watched a group of young people. They were dancing, although the dance was stylized as a fight. The music was mostly rhythms, performed on some kind of a drum. There were two dancers, making attacking movements, or some acrobatics elements. When one was "attacked", another avoided the attack and then attacked himself -- or herself -- it was a mixed group. Periodically one of dancers was changed by somewhere from the circle of other dancers, without interrupting the dance. Then the second dancer was replaced, and so finally they all took part. As I understood, the movements were improvised, so the dancers had to watch what their partner was going to do, to react accordingly - on such close distance movements could easily result in injuries.