The music starts playing right away when a world is loaded. It loops, which is nice and all, but then after it plays once a second song plays at the same time as the first one is looping. Music that plays at sunrise and sunset plays at its respective time, but also loops and overlaps the music that's already playing. Ambient music doesn't stop playing when a music disc is played. Game mode doesn't seem to have any effect. Music also can't be turned down or off by the volume controls.