The in game MP3 player is a nice little addition and almost a requirement for any game coming out after this year the player base loves it and here is how it works.

Hit "esc" then options and check the MP3 player checkbox. Once you have the MP3 player open you have the following options.

1. Display the song title 
2. previous song
3. Play
4. Stop
5. Listen to next song
6. Repeat one song, repeat list
7. Show/hide the list
8. Minimize
9. Close the player
10. Adjust volume
11. Close the list window