While Ingrid Bergman portrays Charlotte the pianist, the person we really see and hear playing is Ingmar Bergman's ex-wife Käbi Laretei, an acclaimed concert pianist. She even acted as Ingrid's body double at the keyboard.
The film struck very close to home for Ingrid Bergman to the extent that she was quite shocked when she read the screenplay for the first time. It deals with a self-centered artist who leaves her children in their formative years to go off and pursue her career. During the late 40s, Bergman herself became a cause celebre by abandoning her family to run off with Italian film director, Roberto Rossellini.
Ingmar Bergman later stated that when they first started shooting, Ingrid Bergman played her part horribly. But after they discussed it, she was "Brilliant, incredibly difficult, but brilliant".