As you know, I am an avid fan and of your methods and this thread has reminded me of the one nagging question I continue to have so I thought I would mention that here as I suspect once others get past what the aperture corners are this may well be the next question that comes to mind. What does “>tension< of the aperture corners” really translate to in terms of the shape change? The dictionary definition of “tension” is “the state of being stretched tight” but this in my mind is not what you are trying to get us to understand/do; especially in light of the comment you make in the ultimate text/video about the embrasure for middle-G is used at all registers. I can accept that from personal experience but “tension” is just a conceptual fail for me. Perhaps some clarification on this would be helpful, maybe even a diagram perhaps showing which way the lip muscle forces are directed?