Hey,

A really good example of how the mood works in a video game is how the mood works in a film. Its sometimes difficult to pick out the subtleties, but for example if two people are having a conversation, and one says something important, a simple low string chord would let the viewer know 'oh man, no way..' if there hadn't been anything there the impact of the conversation might not register with the viewer. Its like that in video games too, I remember I was playing Return to Castle Wolfenstein couple of weeks ago, and I entered a new room, the music got really intense with fast brass sections and lots of timpanis, I just knew that once I stepped through that door I was going to get my head taken off. My favorite trick is the low pad or string section sound, its hard for the audience to put a finger on it, but they know something is up.

-Levan
www.dreamlandscheme.com (my portfolio, I'm a composer )