I have nothing to prove, and I'm not making this up!

Hold on there Foolestroupe - methinks you protest too much; a definite overreaction to what was, in truth, a simply enquiry. I'm curious that's all - and frankly baffled; if this technique does indeed exist then it's the first I've heard of it in 42 years of blowing down whistles, flutes, reeds & horns of all shapes & sizes. Yes I play tabor pipe - and yes I know how French Horns work; I also play clarinet, pocket cornet and have even played Hunting Horns with Hunt Sabs so I know about pitch bending. Some examples of this mystery technique of yours would be welcome...

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Meanwhile, here's a wee film from Sept 2004 I did the music for which features an overtone flute in consort with other folk instruments - koboz, crwth, melodica, ducks, warblers, bells and diverse fowler calls...

http://www.youtube.com/watch?v=PRC75b1NXGI