Instrumental piece in B for orchestra

The Instrumental piece in B for orchestra, KV 638 originated during the grand tour of Western Europe, as evidenced by the paper type and handwriting of the autograph score. The keys of the composition are unique in Mozart’s oeuvre: The piece begins in B major and its second part ends in G-sharp minor. It had long been thought to be a fragment, but part I is to be repeated after part II. The most plausible explanation regarding its genesis is that Mozart had intended this piece for Gallimathias musicum, KV 32. KV 638 was mentioned in earlier editions of the Köchel Catalog only in conjunction with the second version of the Trio to the second movement of KV 186, for which Mozart much later used the verso of the sheet of music paper.