Firstly, angels don't dance. It's one of the distinguishing characteristics that marks an angel. So, none. At least, nearly none […] So providing the dance was a gavotte, the answer is a straightforward "one". Then again, you might just as well ask how many demons can dance on the head of a pin. They're of the same original stock, after all. And at least demons dance. Not what you'd call good dancing, though.