It's always interesting to experiment with computer games without the use of music, but music as tool in game making is very effective to create mood, so I think that one should not refuse to use it.
The mood of the music does not always affect the mood of the game directly.
I used gorgeous music of Taylor Hayward in "Just Close Your Eyes". This music is extremely beautiful, and I used it to create a contrast to static noise. Some people considered this game as "creepy" and, wow, they called music "creepy" too
Another example is in Kubrick's movie "Clockwork Orange", where classical music is played during the scenes of extreme violence