What happens when Sophie begins to sing in the play, Master Class?

When Sophie begins to sing, Maria hears in her mind her own performance as a recording of Maria Callas is played. Her mind goes back to her relationship with the wealthy Greek businessman Aristotle Onassis, whose companion she was for many years. As she reminisces, she imitates Onassis's voice and his crude way of speaking. She has him say that he bought her with his wealth and that she gave him class, allowing him to acquire the respect that had not formerly been given to him. He tells her how wealthy he is and that she can have everything she wants. He wants her to stop her singing career and sing only for him, and he also asks her to have his child.