It is normal for there to be relatively short periods of silence when music for a particular area loops, or when the music changes or (IIRC) the game is saved/loaded. If the music drops out for more than a minute or so, then that might be an issue. In either case, I don't know of a way to tweak music timings.
I do not believe there is anything in the game to allow repeated spell casting (assuming you have the mana). If you have extra mouse buttons, you could check to see if you can assign one to a repeated right click (I'd expect this type of feature with gamepads, but not mice). Games are not designed to multi-task, so macro programs, etc probably would not work (looking for screenshot programs, I was restricted to those that could use the Print Screen key for a hotkey, since other keystrokes were not passed along to background programs).
