400 Hz is one of Barbara Hero's tones, associated with manganese and, in her system, with the pituitary. The same round pitch also turns up among her isotope correspondences, one of the meeting points between her elemental and isotope families. The pairings are Hero's own framework, offered for listening rather than as measurement. Barbara Hero built her work on the Pythagorean Lambdoma, a matrix of whole-number ratios she rendered as sound on a custom harmonic keyboard. Among her explorations was a set of tones linked to individual elements (sulfur, iron, copper, iodine) and paired, in her correspondence system, with endocrine glands. The mappings are her own contemplative framework, not chemistry or physiology. 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.