Interactive Notation Editor based on Vexflow music notation library

Hello All, I need to enhance an existing HTML5/JS application based on Vexflow music notation library. There is a working example of the application [login to view URL] I need to get this application extended with the following features - Possibility of adding additional music staff with possibility of selecting type of musical instruments - Enhanced editin features (currently only allows to add and replace existing note and to delete) - Enhanced play feature (such as play one note, play range, play all or one staff etc.) - Save and Open compositions - Export the music in MusicXML and other standards - Export to MP3 and MIDI You will obviously need HTML5/Javascript skills as well as some background in music theory