I tried all the patches and methods on the forums and I still can't get the music to work. Anyone got any ideas? :(

Seems like a rather stupid thing to do. Just annoying.

HeXen: Deathkings of the Dark Citadel is shipping the 1.0 version. This version is missing an important piece of data in the HEXDD.WAD file, meaning that music will not play. The official patch is available in various places, or you could use iwadpatcher to patch just the iwad if you use a sourceport....

I can install GZDoom to work with Hexen but I can't figure out how to make it work with this expansion. Using the HEXDD.WAD file throws an error. Should I use a different source port?

This game has an updated version of the .wad to fix an issue with the game's music. However, this download uses the unpatched 1.0 version, instead of the fixed 1.1 version. Is there a particular reason for that?