In autumn 1765 Mozart’s family was in Holland, not least at the request of Princess Caroline von Nassau-Weilburg. The fame of the prodigy Wolfgang Amadeus had already reached her so that she “had an extraordinary desire to see this child” (according to Leopold Mozart). The Sonatas for Piano K. 26–31 that can also have a violin accompaniment were composed in The Hague. They were published in 1766 and were naturally dedicated to the princess. An early copy which has nothing to do with Mozart was consulted by the New Mozart Edition as a primary source alongside the first edition. Our Urtext edition revises the musical text, deleting the misleading additions from this source.