Mozart composed his second-to-last piano sonata in February 1789, but it did not become known until five years after his death when it was published as a sonata for piano and violin!
This B-flat major Sonata was excluded from the solo piano sonatas until well into the twentieth century even though Mozart had clearly entered the work into his thematic catalog as “for piano alone,” and the violin part had long been deemed with some doubt.
In the first movement Mozart employs the same material for his first and second themes—a spare, leisurely descent and ascent with a gracefully spun-out continuation—but in between he inserts a bold leaping gesture that abruptly shifts to a serene new idea.
The exquisite slow movement unfolds in a luxurious five-part rondo in which each section is a binary form with repeats. The elegant refrain sections surround two contrasting episodes, the first haunting and gently agitated in C minor and the second a singing melody with broken-chord accompaniment.
The lighthearted final movement adopts a rondo form, and Mozart shortens the concluding return of the refrain and adds a jolly coda based mainly on first episode material with a snippet of the second episode cleverly worked in.
Here is Sir Andras Schiff to play this wonderful piano sonata for you: