Music is there for a reason, it helps to create an atmosphere, a mood set for the player. It can help give extra depth to a particular area. For example in a horror film, when something bad and scary is about to happen, I find that usually you get deep quiet tones to help build the suspense, nothing over dramatic. But asoon as that 'bad thing' happens the music hypes up and is loud and extreme.
I find that games have a slightly different approach, for example; The Sims. Everyone knows the Sims music or has heard it before, and to be honest it is pretty annoying. And because its annoying its memorable, and you find yourself with the damn theme music stuck in your head for the rest of the day. You remember the game because of the music. It's the same with that silly game FIFA. In FIFA there are back ground songs as you flick through the menu and set up your teams. I think this is music that hasn't got out into the world yet and actually gets known due to the game. I find myself singing or knowing the song being played in a shop because it triggers a memory. Yes that song was played on FIFA. (or you cant remember where you heard it and it just frustrates you until your brains fall out) Just to clarify I do not play this game, it's silly and does not have any interest of mine what so ever :)
It is clever how music and sounds help you remember what games you have played and enjoyed. Also through my gaming experience I have found that sounds are used to help illustrate something, for example in children s learning games. Also sounds are used to help praise children when they have done something right. Through out the games by 'Living books' such as 'Grandma and me' (these were my favorite as a child) each item you click on has a select sound that connects with it, and when you have done something right you are praised with a star sound or something like that, can't quite remember.
I feel that games need sound and music to help develop them further and help expand them, it is what makes a good game. If the sound is rubbish and the graphics are good, the sound can make the end result of the game terrible therefor both need to be equal to help each other to make an epic game.