Is there a way, possibly through CMD, for me to mute only one program at any one time? My problem is that a game I am playing on Flash Player 9 has music with it and I would like to be able to listen to my own music on Windows Media Player without the game's music interfering. So can I shut off the flash game's audio and just listen to Media Player by itself?

I would guess there may be an option in the game itself to control the sound.
