Music in video games can not only enhance and a game’s experience and the player’s level of involvement, they can also change it entirely. In the recent 3rd person adventure/combat game Dark Souls, music is used mostly in the traditional lets-be-epic-as-we-kill-stuff manner with choirs, orchestras, etc. See the below video for an example:

(Spoiler Alert) But there is an unexpected twist in the final combat sequence. The mood of the music is completely different–a solitary piano carrying an almost wistful theme throughout the combat. In the game’s story, this final boss is one who’s once good (I think) power has become corrupted, necessitating his defeat and perhaps even the re-ordering of the world (player’s choice). The music seems to denote sadness over the magic that is being lost in the death of this boss–almost as if it were saying “we wish we could have saved it…” See the clip here: