The collaborations of Zbigniew Preisner and director Krzysztof Kieślowski contain an elaborate network of fictional composers and compositions. This network stretches from their first project — No End (1985) — to their last — Three Colours: Red (1994) — and is exemplified most obviously by the fictitious eighteenth-century composer Van den Budenmayer and the pieces ‘by’ him that feature across several films, and the central composer characters and their music in Three Colours: Blue (1993). This chapter focuses primarily on the music, considering not only its functions and effects within the films, but also the processes behind its creation by Preisner, and the manner in which it both emerges from and forms part of his oeuvre. Preisner’s fictional compositions are written ‘in character’, but reflect real-world models and influences. They also point towards future music written in his own voice, and in any case have come to take a central place in the public reception of his work. As well as providing insight into a key facet of Preisner’s activity, examination of this uniquely extensive system of musical make-believe serves to outline trends and theories pertaining to a broader, relatively uninvestigated tradition of fictional music existing across numerous screen, stage and literary texts. This chapter is accompanied in the book by an interview with Zbigniew Preisner, which I conducted by email in mid-2015. The interview can also be downloaded separately: https://link.springer.com/chapter/10.1057/978-1-137-57375-9_4