Prior to 1970 the general belief was that self-hypnosis and hetero-hypnosis were basically the same, the only difference was who was inducing the trance state.
In hetero-hypnosis there is, besides the hypnotist, the subject and the part that is the observer. In other words, the individual's consciousness splits into two. In the case of self-hypnosis, however, the individual must be the director (the hypnotist) the one being directed (the subject) and the observer. In other words, in self-hypnosis the individual's consciousness splits into at least three. In their investigations, all subjects reported more splits in consciousness ("ego splits") in self-hypnosis than in hetero-hypnosis. See also The “Hidden Observer”
In the late 1990’s Ontario, Canada opened the door for anyone to do hypnosis, not just those in the medical professions. Prior to that the same effect was reached through suggestive relaxation techniques or guided imagery. This practice continues in New Age and holistic circles. KNOW THE PERSON doing the guided meditation, whether on CD or in person, WELL.