Extended OSMD, usually exclusive to OSMD Sponsors, with audio player, transposition, etc.
The code and build process works pretty much the same as OSMD, so take a look at the OSMD Readme (and Wiki) for technical info.
To use the TranspositionPlugin, you need the build: transpose-osmd-plugin.min.js.zip Note that this only works with OSMD 0.9.4+.
Here is an example HTML of how to use OSMD + transposition plugin: indexFileSelect.html.zip