Composers face significant challenges in tying together the action of the story with music. In this essay, I look at one tool available, that of key structure, which Mozart used to present a structured narrative to the ever-changing power-balance on the stage. Two primary power sources are in conflict during the finale: on one side, we have the Count, who at the very end is aided by Marcellina, Don Basilio and Bartolo, and on the other side we have the Countess, who receives support from Susanna and Figaro. Entrances and exits of singers constantly interrupt the finale and characters bring new information that tips the scales to one end or the other. I will now proceed by analyzing how tonality is used to express the changing power balance in order to provide the finale with a sense of structure.