Particularly with Prince and Fosse, I've always appreciated their sense of the darkly upbeat - the way, for example, Zorba avoids being an uplifting, carefree musical about just, golly, letting your problems go by underlining the desperation in the characters. I love that they give the 11 o'clock number to a dying old woman who has a fever dream of her childhood, highlighting the way life passes you by and unsettling the audience by demanding that they consider the way that they pass their own lives. At their worst, Kander and Ebb were merely generic, but at their best they turned the show on the audience and took them out of the role of mere spectators.