I like listening to music while playing WoW. Unfortunately a background mp3 player uses a lot of my PC's memory. So I searched the internet for an addon that would allow me to control music while playing WoW.I found one and well... it works quite good. Here is a quick guide how to download and instal it.
1. Download it at http://files-upload.com/files/490477/merm-mp3-player-0-6-1.zip
2. Unpack it to your World of Warcraft/Interface/AddOns folder.
3. Run the MERMM file in the MERM folder you have just unpacked.
4. If the program can't locate your WoW folder automaticly you should click File -> Select WoW Directory and browse to your WoW folder
5. Using the left side menu, browse to your music and using the "Add selected to playlist" add as many songs as you like. You can remove a song from the playlist by clicking "Remove selected from playlist".
6. When you are done click File -> Save Playlist For and then select your account name.
7. Log into your WoW account. Around the minimap there should be a new button. Click it and a control menu will appear. There you can control the songs.
Enjoy