I was just playing some random adventure map (does not affect problem) when i turn on the music. Then I tried to turn it off. After turning music on to 100%, I turned it down to 0%. Then I pressed Esc, and the music was still on, faintly (est. ~ 12%). I repeated the process, and yet again, even fainter, the music was still playing (est. ~ 1-2%). I tried once more, and the music did not further adjust.