Anaerobe’s Permanent Underground, a New United Media product, is a four-part, four-hour epic that straddles the line between sound and silence and plumbs the depths of the barely audible rumble that lies beneath the electronically reproduced sound that permeates the post-industrial landscape of early 21st-century America. Recorded sound is all around us, but what is the sound of electric recording itself? What is the sound of the structural underpinning of the electronically reproduced sound that we so often take for granted? Does this underpinning exist? Is it real or imaginary? Regardless, Permanent Underground attempts to capture what it is, could be, or might be, and the result is both subtle and massive, both barely noticeable and inescapable. This is the sound that lies below sound. It is hard to say where it began, and it seems to have no end. To listen to it in its entirety is to heighten one’s own sensitivity to and awareness of the foundation of recorded sound, and deepen one’s appreciation of all sound, whether recorded or live.