Hello, I know that this is really old and i'm sorry that i'm digging it up, but I've had the same problem, but I found a simple fix by mistake. Almost every CDLC song started too quiet(guitar volume was ok) but It was impossible to hear other instruments, so the fix I found is pretty simple. Press ESC after the song has started(the speakers show up) and just press ESC again and start having fun with normal sound of the song ;) Sorry again for the dig up, but someone may still look for some fix to that.