Michael Haydn composed his four Sonatas for Violin and Viola in 1783, commissioned by the Salzburg archbishop. In fact, the archbishop ordered six sonatas, but Haydn fell ill and was not able to write the last two sonatas himself. As helper in need, Wolfgang Amadeus Mozart aided his friend. He composed the two missing sonatas and agreed that they would be presented to the archbishop under the name of Haydn. While both sonatas by Mozart have found a wide distribution, the four compositions by Haydn nearly fell into oblivion and are made available again with this edition.