Keep in mind that there is positive tension and negative tension. Negative tension, in my mind, is anything that inhibits you from sounding your best and playing all over the range of the instrument. Negative tension can be found in many places such as the throat and especially in the center of lips.
As demonstrated in the videos, the lips do not need to buzz while playing the horn. To prove this to yourself, buzz a note on the mouthpiece. Now do the same thing with the mouthpiece on the trumpet. Now didn’t that sound like a beginner band student who was told that buzzing is the way to play?
Another aspect is there are several successful ways to play. So don’t think that what Greg is teaching is the absolute only way. I am confident that the center of the lips cannot clamp down and push together and be the most efficient method for playing.
Aperture corners can be found by doing the aah-ooh as demonstrated. It is important the corners of the lips have tension. This is your anchor and I find that keeping a stable embouchure firm lip corners are essential, but this is not your aperture corners. These firm lip corners are NOT created by smiling or frowning lips but are located on both sides although there usually is a slight frown when engaged.
Aperture corners are on either side of the opening (aperture). The lip muscles will control the corner tension which will go toward the center as you ascend creating a smaller aperture. Perhaps you have seen a garden hose sprayer, the one that you twist to change the water velocity. Opened all the way, the water just falls out. Twisting the sprayer closes down the opening ever smaller creating a faster stream. Keep twisting and it closes it off and no water comes out. We are not twisting lips to get, but our muscles will allow us to close down the aperture from the sides. This is positive tension that is not the same as squeezing the lip together top to bottom.
I really am apprehensive about advertising a product. I bought Warburton’s P.E.T.E. – Personal Embouchure Training Exerciser. It is an expensive way to establish an embouchure that Greg is describing. You will feel the anchored lip corners and the aperture corners. Follow the instructions and it is easy to get what the embouchure should be. I don’t really exercise with it,
but I go back to it to get the “correct” sensations.