Before I became Catholic, i took training as a hypnotist (shame on me). To the best of my knowledge, I will sum up what I know about self-hypnosis:
In your normal waking state, e.g. when working or reading, the brain produces beta waves. If you close your eyes and daydream, it will produce alpha waves. If you close your eyes and listen to the sound of flowing water (e.g. a babbling brook, or a recording of one), the brain will produce alpha and theta waves. They are part of the brain’s normal repertoire.
The CDs you mentioned are designed to do the same thing. They do not produce “altered states of consciousness”; basically they just pave the way for alpha and theta brain waves. But if you were listening to such a CD and heard somebody yell “Fire!”, your brain’s liberty to resume beta wave thought in order to react to the alarm would not be impaired by the CD.
Normal consciousness includes a variety of different states, including the hypnagogic state experienced as “drifting off” before one goes to sleep (mainly theta waves). Self-hypnosis may lead one into this state of temporary stupor, or may simply induce relaxed (alpha and/or theta) brain waves. If you had to, you could be awake and alert in a heartbeat (though the more relaxed you are, the more physically stressful the sudden awakening would be, like when your alarm clock blares you out of sleep in the morning).
Rarely, I have met people who can put themselves into and out of deep hypnotic trance at will – the kind of trance stage hypnotists use with spectacular results. The stage hypnotist will tell subjects that they are the man who narrates the TV car dealer commercial and that they’re on the air, or that this piece of candy wrapper foil is too hot to touch, and they will react accordingly. But if they have hypnotised themselves they cannot issue themselves such commands. They are in a deep sleep. And that’s what these rare people I knew used self-hypnosis for – to get an hour’s worth of sleep out of a ten-minute hypnotic “nap”. Still, this IS an altered state of consciousness, and I wouldn’t go there if I were you; your normal barriers are down, and you might be open to influences from the spirit world against which your conscious mind would ordinarily defend itself.
But the common relaxation states most people experience in self-hypnosis do not cause you to lose your mental freedom. You are not listening to somebody else’s commands; at most, you might listen to those on a CD whose content you have heard and assented to in a waking state. (So-called subliminal audio messages don’t work, by the way.) And you are mentally and physically able to “snap out of it” at will. There is nothing occult about hypnotic states per se, any more than there is anything occult about the influence of alcohol. The problem comes when one or the other causes loss of mental freedom and moral judgment.
