The son of a friend had been accepted into the Music University in Warsaw to study clarinet. We were talking about the differences in playing horn v. clarinet and I was surprised to learn that they are supposed to maintain as steady a pressure whether playing notes that are high or low.
He then surprised me by introducing me to an x-ray of a horn player’s mouth as he played. Fascinating!
If only as a curiosity, follow the link to the YouTube video: