I havent noticed that, but I’ll try to think about it today / tomorrow and let you know.

I’ve heard people describe the opposite–lowering the jaw as they descend and raising it as they ascend, kind of goes along with the tongue movement aaahhh eeeeee. I think Greg touched on that in one of his videos.

I think the movement(s) I make is simple now. There is tongue movement, but I try to keep my lips as relaxed as possible (especially the middle) and sort of squeeze inward horizontally from the sides the aperture tighter around the air column going through the aperture like a drawstring bag being cinched around a can. I try to employ a less is more approach with playing and feel thats how I achieve the most resonant sound and efficiency, etc. The lips do get a bit scrunched up in the middle at the limit of my upper register, but it seems to be working and it appears thats what Greg is doing when he gets up there. The way I think of it is that I need some meat in the mouthpiece to interact with the air column. Before, I think I used to stretch out my lips, clamp down top to bottom and use pressure while over blowing. Now its more of a cooperative coordination between the air and aperture and tongue like driving a manual transmission.