Possible Clues:

• Play section
• When 'Good Morning Baltimore' plays in 'Hairspray'
• When Sally sings "Mein Herr" in Cabaret
• It comes before intermission
• It opens on Broadway
• When Hamlet's father's ghost appears
• When Maggie calls herself 'a cat on a hot tin roof'
• Play part that follows an overture
• When 'June Is Bustin' Out All Over' is heard in 'Carousel'
• When Hamlet first sees a ghost