There are several different types of ways to create subliminal messages for use within music / audio. It depends upon the purpose, but it is generally a good idea to use several methods in your recording.
Here are the most common encoding methods:
Regular – Beyond Frequency: Standard speed messages, simply placed above the limit of human hearing.
Reverse: Messages are recorded then digitally altered to play in reverse. Although you would not consciously understand the message your mind does have the ability to decode this information quite easily.
Multiple Messages: Playing multiple regular messages at the same time; again although you won’t understand the information your mind can still decipher it.
Blended Into Vocal: The message is played at an audible level, but is masked and cleverly blended behind regular vocals so you are not consciously aware of it.
We use a range of different types of encoding in our albums – we use all the above apart from the Blended Into Vocals type (as our subliminal CDs feature no vocals :)). As a mild form of hypnotherapy, giving a few different types of messages gives your subconscious mind a workout, to gives a few different options, your mind may simply pickup on one variety easier than the other.
With a range of techniques used in each album it makes a more effective subliminal experince, and gives a cumulative effect – the more you listen the more information gets into your mind; the faster the changes will occur, and the more dramatic they will be.