There is no reference to the origin, occasion or a performance of the Sinfonia concertante in E-flat for Violin, Viola and Orchestra, K. 364 (320d) because in all probability it was composed in Salzburg (presumably in summer orearly autumn, 1779): Mozart seems to have had no reason to write about it. It was apparently in Paris that he first had the occasion of giving the genre of the “Symphonie concertante” his special attention. On April 5,1778, he wrote to his father: “Now I shall write a sinfonie concertante for flute wendling, oboe Ramm, Punto horn, and Ritter bassoon”.
Even more discouraging must have been the fact that he hadsimilardifficulties in Paris in having the works performed as he had in Mannheim. After the organizier of the Concerts spirituels, Le Gros, contrary to his promise, did not include the mentioned “sinfonie concertante”in his program.
Mozart had no reason to compose any more for this genre in Paris. After Mozart’s return to Salzburg, he might have been eager to introduce the new genre there, especially since adequate instrumentalistswere available. Also the choice of the solo instruments (violin and viola) in the work presented here was probably influenced by the popularity of this instrumental combination in Salzburg at that time.