The premise of 'Stone Song' is that ultra and infra-sound can be used to influence people's moods and actions; this is fairly well established with the use of sound devices to keep teens from loitering in malls. Elephants use low frequency sound to communicate and may also influence predators' moods. This is the basis of 'In the Valley'
Combine those two with a crew of nasties, oppose them with a Wicca girl and a 'normal' guy. Then throw in the recent announcement that ultra sound can sterilise men; in the hands of Baddies that could lead to involuntary sterilisation of any population group - Moslems, Catholics, immigrants, anyone identifiable as a group they don't like. Coupled with the mood and action influencers,there's plenty to work on. I already have that, very simple to slip the sterilisation possibility in - wow Hitler would've loved that.