Gustav Leonhardt portrays Bach in his only performance as an actor. He is a music scholar of International renown, specialized in the works of Johann Sebastian Bach, and a harpsichord virtuoso whose Bach recordings (both as harpsichord player and conductor) are among the finest to be found in recording History.
The script of the film, adapted by Straub/Huillet, was first offered by the couple to Robert Bresson, that declined the offer saying the film could only belong to them.