Francis Bacon in The New Atlantis of 1626:

"We have also sound-houses, where we practise and demonstrate all sounds and their generation. We have harmony which you have not, of quarter-sounds and lesser slides of sounds. Divers instruments of music likewise to you unknown, some sweeter than any you have; with bells and rings that are dainty and sweet. We represent small sounds as great and deep, likewise great sounds extenuate and sharp; we make divers tremblings and warblings of sounds, which in their original are entire. We represent and imitate all articulate sounds and letters, and the voices and notes of beasts and birds. We have certain helps which, set to the ear, do further the hearing greatly; we have also divers strange and artificial echoes, reflecting the voice many times, and, as it were, tossing it; and some that give back the voice louder than it came, some shriller and some deeper; yea, some rendering the voice, differing in the letters or articulate sound from that they receive. We have all means to convey sounds in trunks and pipes, in strange lines and distances."

Hypnotic Music

by M. Gedde, MD, PhD

They start with soothing "White noise" (similar to ocean waves) which is similar to the visual Ganzfeld effect. This helps clear thoughts, relax and open the subconscious mind more open to suggestion, preparing the way for the next techniques used.
A soft heartbeat sound in the background begins at a frequency of 60 bpm (beats per minute). This has been shown to aid relaxation & learning ability (students may be familiar with the effect via "super-learning" programs. This is also the tempo used in much classical and reggae music. The heartbeat slowly changes tempo over a half-hour period, "entraining" the listeners heartbeat. As the listeners heart also slows down, they relax more, and their mind becomes more receptive and "suggestible" to positive affirmations.
Similar to how a listeners own heart will slow down as it hears another heartbeat slow down, brainwaves do the same thing. This is called "brainwave entrainment". Why is that important? Normal waking state of mind brainwaves associated with being active, less aware, excited, anxious, fearful, "uptight", etc., are quite rapid, upwards from 14 cycles per second. The frequency of AC electric wiring in a US house, is 60 cycles - talk about getting bombarded with high anxiety! The Earth's magnetic field is in the area of 10 hz (cycles per second). Alpha brainwave frequencies are also in that range, and are associated with being relaxed, more aware, and much more intuitive - like being in a very light meditative or hypnotic state (have you ever noticed how it "feels" better, more "calm and quiet" when there is a power outage?). As brainwaves slow down even more, they enter the Alpha-theta frequencies (associated with deeper meditation, creative thoughts and activity, visualizations/visions ), then down to Theta (deeply relaxed meditation master levels, deep contemplation, also out of body experiences, etc.).
Excellent human hearing can only hear low bass sounds down to about 20 cycles per second (a bass drum is about 60, just to give you an idea). But brainwaves associated with deep relaxation, awareness, and meditation, are slower. Thus the brain needs to be accessed in other ways to stimulate those frequencies. One way is flashing lights, another is by using a "clicking" or "tapping" sound. Thus our CDs use brainwave entrainment sounds that start at the normal "awake and active" brainwave frequencies, and gradual slow over a half-hour, first through Alpha, then slower through the Alpha-Theta frequencies, then to Theta frequencies. But that's not the only technique we developed.
Since the beneficial slow Alpha brainwave frequency is so desirable, and can't be heard, we induce it with another highly unique method. We actually stimulate the brain to "feel" and move into these frequencies by creating an audio "interference pattern". What???
Our EMDR -assist sounds CDs actually create a sub-audible "beat" in the Alpha brainwave range that is "felt" inside the head rather than heard, thus stimulating Alpha brainwave production. This is accomplished by using stereo headphones and a stereo CD player. One frequency is fed to one hemisphere of the brain through one ear, and another frequency is played in the other. That creates a "difference" of, and sub-audible beat frequency of, 10 hz.
The conscious mind often "blocks out" things it doesn't want to hear, or deal with, such as traumatic issues or sensitive topics. Instead of using subliminal techniques to get passed the conscious mind "blocking" the sounds or affirmations/suggestions, a unique 3-D recording technology is used to help by-pass the blocking.
Rising and descending frequencies are used to help deepen the state, and stimulate the return to a normal awake and refreshed state of mind near the end of each recording.

For the hypnotic techniques, the following are used:

Progressive relaxation - relaxing parts of the body from head to toe.
Guided visualization - keeps thoughts focused and moving for relaxation and deepening of the hypnotic state.
Classic hypnosis - time-proven self-hypnosis techniques are employed for accessing the subconscious mind.
Positive affirmations - after entering a deep state in which the subconscious mind can be accessed, affirmations are used to help reprogram it to make the desired changes (all different according to the topic chosen).
Hypnotic "trigger words" are used and given to the user, so they can re-enter the deep relaxed state at any time, just by repeating the words in their mind. "Relax, Relax, Relax" is used for anytime someone wants to quickly return to the state. "Peaceful now" is used anytime there is a need to experience calm and feel inner peace. Both trigger word sets are only effective when used by the user, or a trusted friend or loved one (a wonderful aid if injured or ill, and incapable of saying them yourself