Sinfonia concertante in E-flat major, K. 364

Written in Salzburg in 1779, after Mozart's return from the unsuccessful journey to Mannheim and Paris, and shaped by what he had heard there: the wind writing of the Mannheim orchestra and the French taste for the sinfonia concertante. The viola part is notated a semitone lower and the instrument tuned up to match, so that its strings speak more brightly and the soloist is not covered by the violin. No commission and no first performance is documented. The C minor slow movement is a dialogue in which neither soloist is ever merely the other's accompanist.