Hello, Jeannette--
Thank you for the reply.
it's not a formant filter. It's a reed pipe with a resonator. Wikipedia
has this to say - and probably to show on the matter:
https://en.wikipedia.org/w/index.php?title=Vox_humana
My apologies, Jeannette. "Formant filter" was a little misleading on
purpose, more like bait. But now that a couple people have bit, i'll be
more accurate. Ralf's link to organ stops contains a good demonstration of
a vox humana:
http://www.organstops.org/_sounds/CulverAcademy/VoxHumanaArpeg.mp3
It does change formants slightly, but nowhere near as dramatically as the
basilica organ. So then, how did the boys from Weingarten accomplish such
a drastic change in vowels?
i've found a highly technical article on reed pipes. It may be above my
head, but i'll try to read it before forwarding the link.
Thank you, again, Jeannette! Please take care.
Tom