So I was in 14w11b and some music started playing, nothing unusual, but when I decided to test something with redstone I switched gamemodes. And the moment I pressed enter to execute the command /gamemode 0, the music just stopped! Later it started playing music again, by that time, my redstone testing was over, so I switched to creative. AGAIN, the music stopped!
-I don't know if it's switching to all gamemodes, I just found out creative and survival!
-I was in a super flat world with redstone ready preset.
This is all info I have.
This is not a bug. Some of the music in Minecraft only plays when you are in creative. It will stop when your are no longer in creative.