I've also decided to change sax for guitar in every way I can, to swap the medium and hard parts in practice/musicianship to fit what else I'm adding (I may even plug my own guitar in for this!). I'm also adding/changing items for sale for things like backdrop, props, etc..
It also turns out that mp3 support is not available in-game, so I'll find a way to chop mp3s and convert them to Ogg Vorbis. Everything else, bar debugging, is pretty simple. The game will be so rich in new material that testing will be a joy rather than a chore!