i think if not mistaken, in the past, there was some way to change the music device being used by the game, such as using roland MT or adlib. Sounds like by default it is adlib.

i also saw in some websites there was ega version of the game.

does anyone know how to do all these in the gog version?

When you open game it should give you a launcher with the choices of

1. Ultima VI: The False Prophet
2. Game DOS Settings
3. exit program.

2.

It will ask where to install, I don't know if these choices actually mattered, but I picked hard disk and c drive.

Then you get choices of graphics, and sound after that (and asking if you have a mouse in between).

Roland is technically a sound option, but you won't be able to use it by default. It requires files GOG is not allowed to include to emulate it and you would have to find on your own.