Hi,
I have the same problem and was wondering the same thing.
I have trouble “tightening” the corners while leaving the middle of the top lip completely free.
I must be missing something. 🙂
The concept of “No sound” is easy to understand, but that of “No top lip”, as you can hear Greg say in the videos, is less obvious.
It was actually a question I wanted to ask during a Sunday session.
When you only see Greg’s lips and he goes from low to high, the shape of the middle of the upper lip seems more to go against the teeth rather than forward and to be free like a bedsheet.
But it’s not easy to see exactly what’s going on.

Regards
Jérôme – France