C minor is usually the tone of drama, passion, pathos and pain. The same goes here, in this sonata in C minor first order K. 457 written in October 1784 without anyone knowing what could have triggered this incredible explosion of “romantic” sensibility. Six months later, Mozart composed his Fantasy in C minor K. 475, extraordinary in all respects. The two works in C minor were then published in 1785 in a single edition, that is to say that they were deliberately associated by the composer, without any agreement. The Autographs of Fantasy and Sonata in C minor were considered lost until 1990. Just after their reappearance in Philadelphia (USA), the house of Henle was the first to undertake an in-depth revision of the text. In many places the known text had to be subject to revision because until then the most important sources - the first edition as well as an authorized copy of the sonata for dedication thus proved to be imprecise and riddled with errors. Like what, even an "Urtext" edition is sometimes subject to improvement.