Today I thought again of Richard Feynman, physicist and teacher, and his quest to visit the Republic of Tuva, because of his pre-teen fascination with the unusually beautiful stamps of that state. See
Tuva is also famous for its throat singing. The singer produces a continuous low drone and then modulates the shape of the mouth and lips to generate a melody over the top, using the harmonics of the base note. Try steadily humming hummmmm and then moving you lips in the shape of vowel e a i o u, to get an idea.
That is about as far as I can go. But accomplished traditional throat singers can generate a second overtone, so sing three notes at once. Some Western classically trained singers have also learned to produce similar overtones and some pieces have been written for this style but it's unusual.
To hear some Tuvan throat singing visit