GC2 does a good job of managing the music when it looses the focus (in windowed mode) with the exception of minimizing the game window by clicking on the window title in the desktop's task bar. So far, I have heard the music stop (consistant with any other method of shifting the focus away from the game window), stop and start with a fraction of a second of delay, and not stop at all (wich could also be a start and stop without a discernible delay).
