If your game is in mono only when you go to the settings and try to change the audio output (I think it's explained on page 8 of the GH3 manual I dunno) you can only leave it in mono. If your game is a fixed copy, you should be able to choose between mono and stereo (and surround if it supports it). At least, this is what I think.
I don't think Aerosmith has any sound issues.