And When the Music Stops

What is the strange incessant music that keeps Wilhelm and his people, the Hundeiss, in slavery? Living and working underground all their lives, none of them has ever seen daylight. So when a chance rock fall enables Wilhelm to escape into the world above ground - a world he didn't know existed - it is something he neither recognises nor understands. But will anyone believe his story - and will anyone help him on his quest to unravel the centuries-old mystery that will release his people from slavery?