csanjuro: Ultima Underworld Portable, UnderworldExporter or Dosbox?
Not sure what the first two are, but if you are playing the original with DOSBox...
...for the love of god, enable Roland CM-32L music in the game! You will enjoy the game about 100x then compared to the the rinky-dinky Adlib/Soundblaster music, making it much more atmospheric when traversing the dark tunnels...
You will probably have to seek Roland CM-32L ROMs online for that to work. Roland MT-32 ROMs work too but then you will miss certain sound effects within the game that CM-32L has and MT-32 does not, like I think the swimming sound etc.
IIRC DOSBox-staging possibly has built-in Roland MT-32/CM-32L support so you probably only need the aforementioned ROM files for it, while with generic DOSBox (that I believe the vanilla GOG version is using) you'd also need to set up Munt (a Roland emulator) to work with DOSBox.
After that, this is what the game should sound like:
https://www.youtube.com/watch?v=Y1DbftLCwMA&list=PLQfcsYP5T4-GLq6qcvmGTDFOnEwvByiaY https://www.youtube.com/watch?v=1Uii-uSjOqY&list=PLQfcsYP5T4-GLq6qcvmGTDFOnEwvByiaY&index=4 Another tip: don't accidentally push that one old lady to lava in certain level! I think you need her for some important thing or quest, possibly making it impossible to finish the game without her (not sure...).
EDIT: That first "Ultima Underworld Portable" sounds pretty good since it uses DOSBox-staging and is created specifically for the GOG version of the game, and apparently there is also some optional mouselook patch for it (not sure how it works, but UUW 1-2 has similar clumsy and complicated controls as e.g. the original System Shock, and the mouselook patch for System Shock made it much more playable, even for a veteran like me who originally finished it with the original clumsy controls).