The program can play music in the background in slideshow mode. Here you can select the location of the music files (wma and mp3). The operation is very similar to the previous tab (image selection) but here you select the folders containing your music. Additionally there is a slider to control the volume of the music (independent of the general setting of your computer)
Mute will disable playing music and Mute if screensaver will not play music if the program is running as screen saver.