In much more succinct fashion, here are the fixes/upgrades to xu4 that I cobbled together a while back. . .
Here is the music upgrade (featuring Roland Sound Canvas) for the xu4 edition of Ultima IV: Quest of the Avatar. For listening outside of the game, here’s plain MP3 versions. (more info)
There are various versions of xU4 floating around. All of this is designed to work with “xU4 1.1svn” (2/22/2013) which you can download from this part of the xu4 website. You should download the latest “snapshot” build and avoid the “betas” since they are actually much older.