Harmonies occur when two or more notes come together, and create a beautiful uplifted environment. You can read about how harmonies occur and the use of harmonies in therapy in our article The Use Of Harmonies In Therapeutic Sound Healing. In our decades of experience, we know these bowls work well to deepen relaxation and create simple joy. Harmonic intervals have been known and used for thousands of years around the world. Now, scientific research shows that use of such intervals creates deep states of relaxation and wellness. The body's natural neurological response to the perfect fifth musical interval, for instance, is proven to assist in entering states of deep relaxation. We use, almost exclusively, harmonic crystal bowl sets in our crystal bowl sound healing work. Our Harmonic Chord Pure Quartz Crystal Singing Bowl sets are an excellent way to work with Quartz Crystal Singing Bowls without buying a full 7,8 or 9 bowl set. These harmonic connections are found in the 7, 8 and 9 bowl sets, though here we are just selling the most uplifted purest harmonies from those sets. We are offering these harmonies in 2, 3, 4 and 5 bowl sets, in the Key of C and the Key of A. The Key of C is used for the chakra system, so these harmonic sets can be expanded upon in the future to full 7, 8 or 9 bowl chakra sets. The Key of A is lower pitched than the C, and many people find lower pitched notes to be more relaxing, and pleasing to the ears, then higher pitched sets. Please listen to the sound files, and read the content in the product pages to learn more about these harmonic sets. Please feel free to call us if you want clarification or further information on these sets, or if you just would like help selecting the right bowls for your needs, or others in your life!! We look forward to being of service in your sound work!!