as I understand the mechanism how higher notes are played, the aperture corners move inwards. This results in a smaller diameter of the aperture in right/left-direction.
But this can only be done to a definite extent- then the aperture is obstructed. In any case this is the experience that I make: when I go up, beginning around c2/e2 the blowing resistance increases, the result is that it is not possible for me to produce a tone by passive reduction but I have to support actively.
To sum up: Isn`t it inevitable that the blowing resistance goes up when the aperture is obstructed by inward-moving aperture corners so that blowing by passive reduction must have a limit when going up.
Everything has a limit and we are simply working on extending your limit.
Your proposition that eventually the width will be so narrow that the “aperture will be obstructed” suggests a clamping down of the lip tissue which of course is not the idea. The centre of the lip, however small, can remain responsive. Whilst your idea makes mathematical sense, it doesn’t need to go to that extreme to get in to the altissimo register.
It is possible play G above high C and above with no exertion below the head ie. simply using the air in the mouth cavity. Sure, it will be a very short note and get incrementally softer as you ascend but it can be done.
Working through the 6 Steps of the Singing C Series will extend your limits. Just take it a semitone at a time.
Thank you, Greg, this makes it much clearer to me.
So the loose center is the primary goal to achieve and the subtle alterations of the aperture corners must let the responsiveness of the center be unaltered.