426.7 Hz is the note A built from scientific pitch, seated at the third eye, the chakra of insight and inner sight. (It sits close to, but is distinct from, the separate A = 432 tuning movement.) It is used as a still, focusing tone for inward attention. Setting middle C to exactly 256 Hz ('scientific' or 'philosophical' pitch) gives a scale whose octaves are clean powers of two. Sound practitioners favour it because every chakra then lands on a tidy number: 256 at the root, doubling to 512 an octave up. Reading the white-key scale upward, one note per centre, produces this seven-tone chakra ladder. Independent of any tradition, controlled clinical evidence that a specific frequency produces a specific health effect is limited and mixed. Auriviel presents these tunings as music and contemplative practice. This page is for general information and relaxation. Auriviel's frequency music is not medical advice, diagnosis, or treatment, and no health outcome is claimed. If you have a medical concern, please consult a qualified professional.