From MangaHelpers:

This is a fictional re-telling of the life of Wolfgang Amadeus Mozart, with a new twist. Mozart was actually born a girl, but her father chose to pass her off as a boy when he witnessed her early genius in music. The main story begins when Mozart is 25, working successfully as a musician in Vienna. "He" is wildly popular, especially with the ladies, but "he" mostly avoids them in order to protect the secret of "his" gender. Unfortunately, another local composer, Antonio Salieri, suspects that Mozart is actually a woman. When Mozart begins courting a girl, Constanze Weber, it seems impossible that "his" secret and career will endure! [tethysdust]