The Kingdom of Back by Marie Lu

His brilliance begins to eclipse her own, until one day a mysterious stranger from a magical land appears with an irresistible offer. And as Nannerl's hope grows dimmer with each passing year, the talents of her beloved younger brother, Wolfgang, only seem to shine brighter. She will perform only until she reaches a marriageable age-her tyrannical father has made that much clear. She is a young woman in 18th century Europe, and that means composing is forbidden to her. But even as she delights audiences with her masterful playing, she has little hope she'll ever become the acclaimed composer she longs to be. Born with a gift for music, Nannerl Mozart has just one wish-to be remembered forever.

From #1 New York Times bestselling author Marie Lu comes a historical YA fantasy about a musical prodigy and the dangerous lengths she'll go to make history remember her-perfect for fans of Susanna Clarke and The Hazel Wood.