Steve,

Just posted links to a couple videos in another thread; thought I would post them here as well.

This is me doing harmonic slurs, trying to focus on tightening my aperture from the corners as I ascend–which is easy if I tighten the corners, but difficult if I do what I used to–clamp down my lips top-to-bottom in the middle, cutting off the vibration of my top lip.

https://youtu.be/fKs9YCczOgM

Here’s another video, FWIW, of an idea I had to help solidify the understanding of tightening the aperture corners–although the videos in Largo, I think, don’t get any better for that. It’s all in there–each time I re-watch, I understand more and more.

https://youtu.be/oQpa3v9bC9E

Hope that helps, FWIW, all my best,

John