Reinforced harmonics

Un-nasalized
“Technique of reinforcing or amplifying specific harmonics of a sung fundamental by adjusting tongue and or lips to change the shape of the vocal tract. The harmonics are perceived as discrete pitches which sound like whistles. Highly developed in Mongolian culture.” (Leonard, 50)

“Harmonics present in a sung tone can be individually reinforced or amplified and perceived as discrete pitches (sounding like whistles) as tongue and/or lip action changes the shape of the vocal tract” (Kavash, 1-2)





Reinforced harmonics are produced by a tongue or lip action which changes the shape of the resonator, fundamental pitch sounded without vibrato.

“The vowels [u], [o], and [ɔ] produce lower partials; [a], [ɛ], and [i] the higher ones” (Leonard, 53)

http://en.wikipedia.org/wiki/IPA_vowel_chart_with_audio

Nasalized
Greater clarity of the harmonic can be achieved through nasalization, filtering out fundamental and focusing harmonic.



Additional
Harmonic oscillation — one manipulates the tongue to produce fluctuation between two harmonics

See: Multiphonic, Overtone Singing