   How to grab the sound that the computer plays?
  We want to create a small software in which 3D dancers dance with music. So we want to grab the sound that the computer currently plays. So that we can analyze the music and find out the beats and rhythm. We have acheived this upon a known music, but we can't know what the computer currently play.Any idears?   
  Most of the mainstream audio libraries provide sound input and basic analysis already, so start looking at them to begin with. (BASS, OPENAL, FMOD, etc)