String Trio in B flat major, K.266

The Divertimento for String Trio in E♭ major, K. 563, is a string trio written by Wolfgang Amadeus Mozart in 1788, the year in which he completed his last three symphonies (nos. 39–41) and his "Coronation" Piano Concerto. It is his last divertimento and different from his other divertimenti not only in its instrumentation but also in its compositorial ambition and scope.
The work was completed in Vienna on 27 September 1788 and is dedicated to Michael von Puchberg, a friend and fellow Freemason, who lent money to Mozart. The premiere was in Dresden on April 13, 1789, with Anton Teyber taking the violin part, Mozart playing viola and Antonín Kraft playing cello. At the time Mozart was conducting a tour of German cities, on his way to Berlin (see Mozart's Berlin journey).