Music is a great way to pass time in real life, but have you ever passed time in something that you are passing time in? That is probably worded very awkardly as I am tired as an 18 wheeler (git it?), so you can just answer the question now.
As for me, I will listen to music in games when things get repetitive, nothing important is happening, or I am going long distances. Certain games have good soundtracks or have an immersion factor that I want to feel, but in a game like, say LittleBigPlanet where everything is in text boxes or GTA 4 where I generally just goof around and don't care what the in game characters say as Niko blows 'em up, I will mute it and listen to some good music to go along with the awesome game.
As for me, I will listen to music in games when things get repetitive, nothing important is happening, or I am going long distances. Certain games have good soundtracks or have an immersion factor that I want to feel, but in a game like, say LittleBigPlanet where everything is in text boxes or GTA 4 where I generally just goof around and don't care what the in game characters say as Niko blows 'em up, I will mute it and listen to some good music to go along with the awesome game.