Overtone Singer Anna-Maria Hefele08/04/2016August 4, 2016Starting with an undertone, Anna-Maria Hefele uses special mouth and tongue movements to filter out sound frequencies. To the ear, it sounds like two separate tones. Millions have seen her on YouTube.Copy linkImage: Thomas RadlwimmerAdvertisementOvertone singer Anna-Maria Hefele04:20This browser does not support the video element.
