Mass Gains

The name of the muscle please. I am trying to cataloge all the muscles involved in a flute embouchure (man there are a lot), but I can’t find the one that draws the corners of the mouth in.
I put this in medicine because i figured that’s were the anatomy people would be lurking.

What is happening to a muscle when you are pushing or pulling on an immoveable object?

A. The muscle is lengthening as in eccentric contraction
B. A concentric contraction is when your muscle is producing more force than the resistance you are using
C. The muscle is neither lengthening nor shorting as in an isometric contraction
D. An isometric contraction occurs when there is a contraction of the muscle, but there is no movement