Hi Patrick, thanks for posting as this sounds similar to “problems” (development opportunities) I’m finding. What works well for me is the ‘milk spout’ aperture and also the 2 fingers placed vertically to strengthen the pull-in of the mouth corners. I’m not sure whether I’m forming the aperture correctly, but I do find that by getting the mouth/lip corners held tightly in an “in” position, the ‘milk spout’ shape forms naturally and note/lip flexibility is then easy. Controlling the aperture corners is easier, I deduce, because the lip ‘corners’ are stable (at least in my case if only temporarily).
However, I think the issue I’m having is that having previously always played (on-and-off for 45 years) without any thought of keeping the lip corners firm and using the aperture corners to flex the pitch, I find my ability to keep the spout shape in place is really hard (it can go in a few seconds). I recently started to focus on this positioning much more and it is helping, but I’m now finding what I think is a lactic acid build up in the jaw ‘hinge’ area. I’m rather hoping this is showing that I’m doing something right, but possibly only time will tell. Its difficult to know how much to push the strengthening exercises and how much to just let the strength come naturally, but as gigging and band/orch rehearsing is now coming back I need to have some playing chops however they work.