Violin Sonata No. 21 (Mozart) is within the scope of WikiProject Classical music, which aims to improve, expand, copy edit, and maintain all articles related to classical music, that are not covered by other classical music related projects. Please read the guidelines for writing and maintaining articles. To participate, you can edit this article or visit the project page for more details.
"It is the only instrumental work by Mozart whose home key is E minor."
Though not for lack of trying: see the string quartet fragment KV 417d. Double sharp (talk) 13:26, 9 February 2016 (UTC)