In the game Overgrowth there is a feature where, depending on how dramatically you are fighting, the crowd sound effect will become louder and higher pitched. A lot of games already do similar things with sound but something about how realistically this crowd blends in stood out to me. Here's a video.
There are a lot of possibilities that could branch off from this, like music that automatically gains more instruments based on how tense a fight gets. Theoretically an entire song could be generated for different situations in a game. Have you ever heard of someone doing something like this?