Voice

Voice is an audio-neuro control mechanism, perfected by the Bene Gesserit out of several advanced techniques trained together. An adept alters the tonal qualities of what she says, gives a simple instruction in that register, and an uninitiated listener carries it out. It is used to make an unwilling person do something they do not want to do, and to get the truth out of someone determined to keep it. Enough natural ability and training make a person more resistant, and technology such as the Cone of Silence blocks it outright. Jessica Atreides weighed using it on Duke Leto himself over decisions about the welfare of House Atreides, subtly enough that he would believe the choices were his own. Against Gurney Halleck she reckoned it would be too difficult to be worth trying.