Is anyone familiar with this sonata? It is listed in the Appendix (Anhang) to the Köchel catalogue, although it is sometimes numbered as K. 498a in the main list.
The circumstances of its composition, and even its authenticity, are in some doubt. The four-movement structure is unusual, and some parts of it have similarities to certain themes in Mozart's piano concertos. There are also stylistic differences between the movements. For these reasons, it is not included in the regular canon of Mozart's sonatas. It used to be included in the Associated Board's collected edition of the sonatas, but is no longer so.
I love (and play) the 1st movement of this sonata. I am impressed by the long arching phrases, and the sheer number of quick notes that Mozart (if it was he) manages to incorporate into the piece without any sense of mere decoration. Every note plays its part in driving the music single-mindedly towards its destination.
I would welcome any comments or background information about this piece, and details of any recordings of it.