In a musical, you will generally see an emotional shift right before the end of Act One. The stakes need to change. One of the most effective examples is from "Kimberly Akimbo." Right before the curtain, Kim decides that she is going to make a birthday demand: If her parents really want her to have a good day, they can promise to be different people. (Less drinking, less self-absorption, less flakiness.) Kim is essentially a child; she thinks these sorts of promises have value. We, in the audience, can sense a trainwreck in the future. Terrific dramatic choice. Another celebrated example is "Defying Gravity." Elphaba realizes that the Wizard is not what he claims to be; she decides she will wage war to free the animals of Oz. The song should feel both exhilarating and nightmarish. Hard to beat the flying, belting Elphaba. "Six" does something unusual. We don't get a curtain that "divides" two acts. But--really--there is a curtain. It falls ...