Until Blizzard gives further notice, this AddOn is broken. The PlayMusic API function no longer works with custom sound files located in the AddOns directory.

See the following threads for information:

• http://us.battle.net/wow/en/forum/topic/13778228089
• http://us.battle.net/wow/en/forum/topic/13421662064?page=3#43

Also note file comments on the EpicMusicPlayer AddOn.

Blizzard fixed PlayMusic in patch 6.0.3.