Sadie
I think what LigH is saying... follow the link, which says to add the following line to the art/soundlib.xml file, just before the </Sounds> XML tag, it's right at the end of the soundlib.xml file...
file="/planeshift/art/music/battle/main.ogg" /> <!--LOOPSTART="-321615"-->
If this works for you, please let us know, because it didn't work for me.