Science on video games

[Prelauncher]

You mentioned music and this might be a bit off topic, but why is music such an important ingredient for the atmosphere in games? I know that it is important and I don't have anything against it but isn't the atmosphere in a game suposed to make your brain believe that what you experience is "real"? So how come music adds to this feeling of connection to the game when there is no music in real life that tells our brain what mood we should be in? It should break the immersion and not strengthen it?