Like her younger brother, Maria Anna Mozart was a child prodigy, but she stopped performing aged 16. In her new documentary, Mozart’s Sister, writer/director Madeleine Hetherton-Miau explores the fascinating theory that Maria Anna perhaps played a bigger role in Mozart’s music than previously thought. She talks to Harriet Cunningham.

Maria Anna Mozart holds a quill at her desk.
A still from the documentary Mozart's Sister with young Maria Anna Mozart in her study. Photo © Shannon Ruddock

“This is the tale of two extraordinary children . . .”

So begins Mozart’s Sister, a new documentary film that tells the intriguing story of Maria Anna Mozart, the sister of the infinitely more famous Wolfgang Amadeus Mozart. Maria Anna, or ‘Nannerl’ as her brother calls her in surviving letters and diaries, was Wolfgang’s...