The music patch works great, but music plays waaay too slowly, even with high cycles. Furthermore, if I increase the amount of cycles, all the animations are way too fast.
To allow for Ultima IV to load with music, the patch creates a U4.BAT file that you have to load in place of ULTIMA.COM. I balanced out the speeds of the music and animations by editing U4.BAT to make use the MOSLO.COM program included in the patch.
So in U4.BAT, the line
"ult4.com"
was replaced by
"moslo.com /20 ult4.com"
to load the game at 20% speed.
I also had to set the number of cycles to 650. For the GOG installation, the cycles can be set in the dosboxULTIMA4F.conf file. Also, the second last line in the .conf file ("ultima.com") has to be replaced with "u4".
So the game is even more awesome than before! It loads a bit slowly and the animations are slightly faster, but it's still close to the original.