This is one of the best ideas and the best lay-out I have ever seen!
Here is another suggestion: while using training method A which is holding the instrument people should be able to request a song. They can only request songs you have unlocked in your music list and if you accept you start playing that song for everyone who ''joins'' you. Obviously the regular playlist would be paused while listening to a player playing a song.
Why? Because it is fun for roleplaying and socializing. It also makes sense.
Remove TH, and put stuff from TH to Solomon's store as guarantees. No disappointment to the average player who only uses free keys which yield trash, and those who do buy into MTX can have a clear idea what the thing they want is going to cost them.