Nicely done! Do you consider synchronizing scores with recordings on YouTube?

We've built a similar thing at http://particellissima.net at the Classical Music Hack Day in Vienna.

It's a demo, but you may find some UI ideas interesting, for example synchronization and navigation through a video, flowing score, hiding the instrument parts that are not playing for a while, and assembling a score from small pieces with measure images hosted on multiple subdomains to improve the fetching performance in the browser.

And of course more music would be great!