[BBvideo 425,350]http://www.youtube.com/watch?v=4iFDPEO6vYA&feature=feedlik[/BBvideo] Some people says that this song is called Chaos (appear in Full Co-Op trailer video). So i post this video because it uses it without any type of voices. ALSO, GOOD JOB VALVe!!! That track reminds me of the Prodigy.