Overtone singing is when a vocalist sings two different notes at the same time. It sounds like something a higherform of intelligence (think Aliens, but without the scariness) might have to try and communicate with earth. The mid and high range keys are in harmony with each other, yet there is a resemblance of some form of oldtime radio wave.
This intriguing form of vocal display is illustrated beautifully by Anna Maria Hefele, a German polyphonic singer who is gifted with the ability to overtone sing. Her explanation and illustration of overtone singing is very well done, especially in showcasing how overtones work with scales.
I’ve seen overtone singing before in a concert with Bela Fleck and the Flecktones and a Tuvan throat singer named Kongarol Ondar. However, Ondar seemed to just sing the same one or two scales during the performance. The skill is amazing, but Hefele has completely transformed the method and style to be able to create various melodies and (vocal) arpeggios within the overtone capacity.
The great skill of singing a high note and low note at the same time, all within a select scale seems impossible, even after both seeing and hearing it. For Hefele, it’s merely one piece of her musical skillset which also includes instrument performer of piano, mandolin, and harp. Her studies and training in polyphonic overtone singing date back to 2005.