Modern science is only now beginning to recognize what the ancient mystics and wise men have told us for centuries; that everything (including you) is in a constant state of vibration. The most elemental state of vibration is that of sound. Everything has an optimum range of vibration, and that rate is called resonance. When we are in resonance, we are in balance. One way to use sound to heal the body is to recognize that every organ, and every cell, absorbs and emits sound, and has a particular optimum resonate frequency.
Emotions and mental states also have certain resonant frequencies; this is the secret behind the transformative power of spiritual music and songs, spoken prayers and mantras. When exposed to a resonant frequency long enough, the body (and mind) will fall into sync; if you have ever been to a large rock concert or a rave, you will understand this. If you sing in a choir, or regularly meditate with mantras, you will intuitively understand this too, because you have experienced it. Therapeutic sound and sound therapy techniques are used to realign the “out of sync frequencies” you may be experiencing within you mind or body, by exposing you to the optimum frequencies for the changes you wish to make within yourself.