A great music. It tortures you to the deepest, it makes you cry. What are happiness and unhappiness? They Don't matter here. You are lost at the moment you listen to it and it's dangerously peaceful.
Well, great music, when it's done right, you can't do anything but to just let it absorb you and take you along for a ride. You have no choice but to concentrate on what's being said, the mood being conveyed, the give-and-take between the instruments. In the end, great music makes you want to go back to the beginning and relive what you just experienced. That's my definition of great music.