Music might set the mood, the themes and the emotions of players if used well in a game, whilst sound effects bring movements and actions in the game world to life. Seeing someone running through snow or across a gravel track just doesn’t seem right unless you can hear a crisp snow sound or crunching gravel beneath their feet.
Example of a music setting a mood is in this game: Call Of Duty Advanced Warfare
The mood that is created by listening to this song is makes you feel like you are gaining the power to play and it fits to the genre of the game as it is a shooting war game.