Look, This is part of the Trio of Daily Calisthenics exercises from the Pivot System developed by Dr. Donald S. Reinhardt. 1. Buzzing Routine, 2. Jaw Retention Drill, 3. Pencil Trick. This only a small part of the package. It is basically designed so you don't place the mouthpiece on your face without some firmness to your embouchure. I've been familiar with this routine since the 1970's. Bobby Shew's 5 minute warm up has the same goal. Reinhardt, to my knowledge, never implied that doing the pencil trick would improve your range.

There is so much misinformation around the internet, including thise site sometimes, that people don't even know the origin of it. Reinhardt also never told people that the pencil trick replaced practice.

I have a couple of good friends that studied with Reinhardt and are excellent players. They didn't walk around all day with a pencil in their mouths. The Warburton P.E.T.E. is an expensive "pencil." Dismissing or misrepresenting the intent of this simple drill only adds to the incredible BS on the internet.