Closely related (basically the same niche audience) but with a completely different approach is my Sheet Music Library plugin (complete, needs a few tweaks before publishing), which is a custom post type with several taxonomies that works primarily off of PDF sheet music and audio recording uploads. It'll work better for larger pieces, whereas this plugin is likely very useful for short excerpts and ideas; gives me a few ideas for use cases, in fact!

My plugin powers my sheet music library: http://celloexpressions.com/music/. I can send the beta version to anyone interested that contacts me, more details here: http://celloexpressions.com/blog/new-sheet-music-library-the-story/. IT used pdf to image conversion to display preview directly on the site, linking to PDF downloads for the whole thing.