I was playing Minecraft, when I realized I heard the Minecraft default music playing. I went to my Options and shut off all sound. Music/Ambient Enviroment/etc. Yet, the music continued to play. I restarted Minecraft, and it was still playing. I then left Single Player and it was still playing at the main menu. It's seems to be an issue only in Single Player, as it has yet to effect my Multiplayer experience.