I fully agree with Edvard, save for the ear-popping being comfortable. On that topic I declare him crazy, as it is a bloody annoying thing if you end up having to do it with any frequency.
Basically the problem is that the theory works, but that practice has far too many variables for it to be implemented in as perfect a manner as we would like. If you assume you have a single sound source
that blasts sounds about, you would at the very least need to know exactly what sounds
are played at exactly what moment
, which is a near impossible task on its own. Additionally, one would need to know the angle/position of the sound source compared to ones ears. Now imagine adding multiple sound sources. Or varying the size, shape or materials of the walls of the room, which determine how sounds bounce around.
Congratulations, at that point you have a system that works in a single room with pre-determined sounds being thrown at you. All you need now is a plug in the elevator for your headphones to get the anti-music from.