New submitter Tucano writes The overtone singer Anna-Maria Hefele can sing two notes at the same time. In her latest video, spectrograms and frequency filters are used to explain how she can produce two melody lines at the same time, and how she uses her mouth to filter the frequencies of her voice. When the voice produces a sound, many harmonics (or overtones) sound at the same time, and we normally hear this as a single tone. In overtone singing, the mouth filters out all harmonics but one, and the one that remains is amplified to become louder. This is then perceived as a separate tone, next to the fundamental. In her video, Anna-Maria shows techniques that become increasingly advanced. She shows the overtone scale (steady fundamental, moving overtone), the undertone scale (steady overtone, moving fundamental), parallel movement and opposing movement of overtone and fundamental, and even complex compositions with two separate melody lines. Read more of this story at Slashdot.

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Polyphonic Overtone Singing Explained Visually With Spectrograms