The belligerent king wants to put the composer to the test and gives him a theme for improvisation, that he has previously had refined by his flute teacher Johann Joachim Quantz, who also teaches Friedrich's sister Amalie.
For example, Friedrich's father executed his childhood friend, Lieutenant Hans Hermann von Katte, after his adolescent son tried to escape with him.
Amalie wants to continue the relationship, but Wilhelm Friedemann refuses to take her to Halle because he cannot offer her a life there that is appropriate for a princess.
Nevertheless, a more personal conversation takes place between the two of them, in which Friedrich tells the musician about the humiliation of his father in his childhood, while Bach accuses himself of having failed in bringing up his quarreling sons.
When Voltaire arrives to Sanssouci at the wish of Frederick II, Bach gets into the carriage at the customs station in his place.