Well, M Ted,

your response supports my theory that it is done with overtones - the intervals you state are all overtones of the fundamental - especially the "out of scale" note - this is one of the overtones omitted from the Pythagorean series. Bugle and cornet players should know about these... :-)

Would be interested if you CAN manage the tone colour change without the pitch change - you would have to restructure your vocal path "on the fly" - but human beings can do amazing things that one might think they couldn't - please let us know when you are well enoigh to try without straining anything.

I would suspect that there might HAVE to be a break...

Robin