Music can be a distraction, an unnecessary layer of sound that pulls attention away from a game rather than enhancing it. Sometimes, there's nothing to do but turn the music off.
The first big-budget game that made me turn off the music was Fallout: New Vegas. I played for a handful of hours and found myself feeling smothered by the endless mournful strings and guitars that played as I wandered the wastes. Every time the music would stop, I'd hear the wind in my ears, the chirping of insects. The desolation around me felt palpable; it was a breath of fresh post-apocalypse.
And then, the music would start up again. Endless syrupy strings and mournful guitars.
So, I turned it off. I never play that game with the music on anymore (though I do still listen to the excellent in-game radio stations). In fact, when I go back to Fallout 3, I do the same thing.
I think it's something about open spaces, at least for me. I adore Bill Elm and Woody Jackson's music for Red Dead Redemption, but sometimes I just don't want to hear music in that game. I want to wander the prairie, me and my horse, and take in the fantastic sound design, which I've long thought to be some of the best of all time. The sound design is almost a musical score of its own; and while its interplay with the dynamic music in the game is organic and never feels crowded, sometimes it's cool to just listen to the audio on its own.
(Seriously, I recommend doing that. Even if you haven't played RDR in a while. Boot it up, turn off the music, and put on headphones. Go sit on the prairie, close your eyes, and listen. Notice every sound that comes and goes. It's really cool.)
Sometimes I'd turn off the music in Bioshock and Bioshock 2, as well. As amazing as the music in those games was, there were times where exploring Rapture while taking in the ear-bustingly incredible sound design was enough.
Is it a sin to turn off the music in a game? No. I remember a while back, boss-man Stephen Totilo wrote a thoughtful editorial about how he finally decided to turn off some games' music.
He, too, found himself turning off the music to Red Dead Redemption, though he was doing it to listen to podcasts while playing. I've met a lot of people who do their podcast-listening while playing Minecraft, and while I personally love the music and audio to that game, I can also understand turning it off and listening to other things.
Stephen also mentioned listening to podcasts while playing iPhone games, and there I agree with him as well. A while back, I played an obscene amount of Bookworm for the iPhone, but I found that in very little time, the music made me go a little bonkers. It took me far too long to realize that I could listen to whatever I wanted while I played, particularly as I was playing on a device that held my entire music collection! But rather than any albums I owned, I listened to podcasts.
In difficult action games, I'll find that the music makes it harder for me to focus; in fact, the audio in general can be overwhelming and distracting. When I get stuck on a particularly difficult boss in, say, God of War II or Bayonetta, I often find that the only way I can make it through is to take off my headphones or mute my speakers and play with no or very low audio. Suddenly, things feel far less complicated and I'm able to focus on the task at hand. It's sort of my last-ditch technique for getting past a frustrating boss.
I'm the last guy who would ever make some sort of sweeping generalization about video games not needing music. Music is an essential part of life just as it's an essential part of all of my favorite games. More than any other aspect, is the thing that ties me emotionally to video games in general.
But sometimes, I just need to play without it.
I'm guessing it's not just me, so I'm curious: What games inspire you to turn the music off?