I play for about 3 hours a day, on a Buffet RC, walter grabner AW_PERS
mouthpiece and vandoren V12 #3,5 reeds. i recently started to experience
biting in the lower lip while i practise. I think it began when i started practising more in the high register (up to altissimo G, sometimes higher).It doesnt ache all the time, but when it does I try to eliminate the problem by loosening my lower jaw from my lower lip. I sound incredibly sharp when i try to do that, and my intonation is ruined (about 40 c too low). where lies my problem here?
Well, first, I would suggest that you don’t practice in the altissima
register above high G for more than a couple of minutes, especially if it gives you difficulty.
You should not change your embouchure when moving into a different register for it is possible and preferable to keep the same embouchure all the time.You seem to use the word “sharp” for being out-of-tune, when it is simply being too high for the prevailing pitch, and flat is below the prevailing pitch.
You cannot say you are playing sharp and below the pitch at the same time, as you say in your note.
In any event, practice in the most favorable register of the clarinet in order to be comfortable in your embouchure, and always use that embouchure, the one that gives you best pitch,sound,attack,staccato and use that embouchure throughout the clarinet.
There is nothing particuarly wrong with the setup as you describe it,
however there is with your embouchure in that extreme high register,
therefore play always with and for your most beautiful sound and embouchure, and the rest will take care of itself, especially if you are playing correctly.
Perhaps you might say that this is not much of an answer but I tell you that
I have heard many many play with the problems that you describe and it is always always the same . Keep the sound always beautiful and correct. There is also nothing wrong with resting your lips and mouth when it gets tired.
Don’t repeat endessly until pain comes, because then you are just playing too much without thinking of what and why.
best in all your work,