Those wishing to get to know Mozart’s gentle, slightly elegiac side should play the opening movement of this lesser-known piano sonata K. 570. The second movement, too, marries the calm strains of horns with a somber melody in C minor. Only in the spirited B-flat major finale (“Allegretto”, in alla breve meter) does the mood shift to – restrained – gaiety. Strangely enough, this sonata was initially published (posthumously in 1796) as a violin sonata, a version that is not at all hard on the ea...