261.5 Hz is one of Barbara Hero's isotope tones, which she associated with uranium-238 by rendering its numeric signature through the whole-number ratios of the Pythagorean Lambdoma on her harmonic keyboard. The pairing of isotope and pitch is Hero's own contemplative framework, a way of listening across scales, offered as sound and never as a measurement of radioactivity or a statement about health. Alongside her elemental tones, Barbara Hero derived a family of pitches she associated with isotopes: uranium, thorium, radium, plutonium and their kin. Rendered through the Lambdoma's whole-number ratios, each becomes a distinct audible tone. As with all of Hero's work, the correspondence is an artistic and numeric system, offered for listening rather than as a measurement of radioactivity. 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.