I believe that this is a psychological experiment in a way. I noticed, even while under, there were no commands or "seeds" as he said put in place to induce nightmares. instead, I believe the "Seed" he planted was at the very end, when he tells you he planted a seed. My guess is that part is intended to get you thinking about it so much that you psyche yourself up *into* having a nightmare. With my experience with hypnosis, though, I haven't had anything happen to me without something a little more direct than what was givent through this sound. I may be wrong, though, this may be something more than tricking your mind into thinking a seed is planted into it (which is practically hypnosis in itself in a way)