Overtone singing, also known as overtone chanting, or harmonic singing, is a type of singing in which the singer manipulates the resonances (or formants) created as air travels from the lungs, past the vocal folds, and out the lips to produce a melody.

The partials (fundamental and overtones) of a sound wave made by the human voice can be selectively amplified by changing the shape of the resonant cavities of the mouth, larynx and pharynx.[1] This resonant tuning allows the singer to create apparently more than one pitch at the same time (the fundamental and a selected overtone), while in effect still generating a single fundamental frequency with his/her vocal folds.

Another name for overtone singing is throat singing, but that term is also used for Inuit throat singing, which is produced differently. – Wikipedia

I have collected a variety of examples, from traditional, to experimental modern forms, and beyond.