Paul Henreid could not play the cello. While he was able to fake it in the long shots, to achieve the illusion in closeup, he wore a special jacket with no sleeves and holes for two real cellists to insert their arms - one to bow, and one to accurately finger the music - while seated behind him, out of shot.
Though a big hit at the box office, it was so expensive to make that it lost half a million dollars; the first Bette Davis movie to lose money since she signed at Warner Bros. in 1932.
Paul Henreid's cello-playing was recorded by Eleanor Aller (Mrs. Felix Slatkin) while she was pregnant with Frederic Zlotkin. Her father, Gregory Aller, coached Henreid in plausible bow movements.
The part of the Ludwig van Beethoven's "Piano Sonata No. 23 Appassionata", which Bette Davis plays at the wedding reception, was recorded by the composer Erich Wolfgang Korngold, who had been a child prodigy.
After Warner Brothers purchased the rights to the play, Barbara Stanwyck was planned for the role of Christine.