Good question, it will be interesting to see the responses you get.
But it’s important to remember that we must not tense up or restrict our throat or body as we ascend.
The aperture must be reduced, but that could and should be done without any unecessary tension in the throat or body.
There does need to be tension in the aperture corners to reduce the aperture AND to keep it open and in the air column so the lips can vibrate freely in the air column, etc.
Less air moves through the instrument the higher we play, so there is a feeling of lighter air and there is an increase in back pressure which can cause a tendency to tense up the throat and body–but that doesn’t help us; we must resist that tendency and learn in time to stop doing that. The lips will vibrate in the air column if they’re there and aren’t overly tensed.
Leading with the air and thinking of a “heee” tends to help me up high and playing softer, but with good air, helps too.
My $.02 FWIW