This may sound a little strange but what would others think about an option to configure the MP3 player to play different playlists according to what is currently happening?
Let me elaborate.
There could be, say, four playlists: "peaceful exploring", "ship battle, "away team" and "shore leave" for example.
Now you could add your MP3s to these playlists and the game would dynamically switch between these playlists.
You could travel through systems and explore clusters to the gentle melodies of Tchaikovsky and as soon as a fight would beginn, it would crossfade to some heavy metal.
I mean, the game already recognizes when a battle begins as it changes the music internally (or, sometimes, actually starts to play music). For all I care I wouldn't even need a fance GUI. You could just name four playlist-files accordingly and copy them into the game folder.
It would just need an option to turn it on and off.