In a letter written in 1764, Leopold Mozart wrote that his child “plays the most difficult works that we have… with incredible precision and so excellently” and “only 12 years old, is one of the most skilful players in Europe”.

He was not referring to his son, Wolfgang Amadeus Mozart, but to his daughter, Maria Anna Mozart, known by the nickname Nannerl. Born in 1751, Nannerl began to receive music lessons from her father (who was himself a respected composer) at age seven. Her little brother Wolfgang, only three years old, worshipped his older sister, and when their father began her musical instruction, Wolfgang insisted on receiving lessons as well.

Both children took to this instruction remarkably quickly, and just a few years later Leopold took them on a performing tour, playing the harpsichord and clavichord for aristocrats across Europe, and they became a sensation as musical prodigies. They played pieces by the well-known composers of their day and compositions by the precocious young Wolfgang, as well as performing their own improvisations at the keyboard. Leopold wrote of his daughter that “her perfect insight into harmony and modulations when she improvises is so successful that you would be astounded.”

Wolfgang and Nannerl were very close as children. They invented a secret language and imagined a realm called the Kingdom of Back that they ruled as King and Queen. Many of Wolfgang’s earliest compositions were notated for him by his sister, for the younger Mozart began composing even before he could write.

Alas, Nannerl was born into a society that expected her to be a wife and mother, not a musician. Unlike her brother, who sometimes defied their father’s wishes, she was an obedient daughter, and when she turned eighteen she retired from touring. She eventually married a magistrate, but she continued to play the piano and gave private lessons for much of her life. Her brother wrote some piano music specifically for her and continued for many years to send her copies of his piano concerti.

We know that Nannerl composed music, for there is a letter from Wolfgang praising one of her compositions, but none have survived. In lieu of one of her own compositions, here is a piece that Wolfgang wrote for her to perform, the Prelude and Fugue in C, K. 394.