CoreLayeredMusic.xml is the file that handles almost all music.
You could just add your music to the folder (without replacing anything) and copy the xml to your C:\Users\*USER*\Documents\My Games\Elemental directory. You will have to tweak a few things, since the songs are arranged to work together. Like Battle_BG provides the backgrounds beat and such.
Im not sure if you can specify another directory for music files, so you should add it to music and just rename the files the xml points towards.
Of course you could just delete additional entries:
<!--********************-->
<!--** BATTLE THEME 1 **-->
<!--********************-->
<LayeredMusicGroup InternalName="BattleTheme1_Full">
<MusicLayer InternalName="FG">
<FileName>Battle1_FG</FileName>
<Volume>60</Volume>
</MusicLayer>
<MusicLayer InternalName="MG">
<FileName>Battle1_MG</FileName>
<Volume>60</Volume>
</MusicLayer>
<MusicLayer InternalName="BG">
<FileName>Battle1_BG</FileName>
<Volume>50</Volume>
</MusicLayer>
</LayeredMusicGroup>
Altered Version:
<!--********************-->
<!--** BATTLE THEME 1 **-->
<!--********************-->
<LayeredMusicGroup InternalName="BattleTheme1_Full">
<MusicLayer InternalName="FG">
<FileName>Battle1_FG</FileName>
<Volume>60</Volume>
</MusicLayer>
</LayeredMusicGroup>
That way only one theme would play.
Hope this helps ^^
