It is just a simplistic music jukebox script. Even so, this script offers you a curious wave effect if you set the BACKDROP_EFFECT constant to :blur in the PlayMusik module below. It will be active as long as any song is playing in the background.
This is how you can add as many songs (BGM's) as deemed necessary.
In the module you can find a constant called BGM_LIST. There add a new entry by typing: