424 Hz is one of Barbara Hero's elemental tones, which she associated with iodine and, in her correspondence system, with the thyroid. The tones come from rendering Pythagorean Lambdoma ratios as audible sound on her harmonic keyboard. The pairing of element, gland, and pitch is Hero's contemplative framework, a way of listening, not a statement of chemistry or biology. It is an octave-relative of Hero's other iodine tone. 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.