*Game mode doesn't matter, but first noticed in creative.
When game music (Not jukebox music discs) is being played, you can exit the world and enter same/other world while music still playing. Other music is able to start playing then, making 2 game musics play at the same time.
1. Wait until game music plays.
2. Exit the world.
3. Enter to another world/save.
4. Another music MAY start playing.