When children play, they pretend. They try out different personas, give themselves arbitrary constraints to force themselves into creativity, and move in as many fast and exhilarating ways as they can. Play is a test of our imagination and abilities, and although we can play alone, it’s much more fulfilling and interesting to play in a group. It’s fitting that the English verb for making music is ‘to play’, and other languages like Mandarin and French agree.