Oh yeah, I'm quite familiar to this. Back in college, I used to belong to the Affective Computing Laboratory, and there were several studies that revolve around changing a person's emotion by using sound. When used positively, it could have great benefits. As you said, it can be used to calm people, remove anxiety or help people become more productive. On the other, if mishandled, it could have catastrophic effects. Studies on this should be done responsibly. There should be countermeasures in place to fight against rogue agents.