Very well, piece for piece the bumps are ironed out. :)
In 1.2 the music can be deactivated by chosing the value 0 but the other values don't affect the music in the game - in other words: there is no difference in volume between the values 1 and 9 for the music in the game (not the menu music). The correct volume gets enabled only if I interact with a closed password protected door: After I do that the music plays with the volume that has been chosen in the settings - but as soon as I get into the menu and return to the game it's reset and plays loud again.