Many players are using too much lip to lip compression- lip to lip closeness to play high C
meaning your chops [face] are not strong enough
to use less lip to lip compression thereby keeping the lips open enough
to expose red lip flesh to allow for easy vibration to use as an endurance cushion (donut) and allow higher notes to vibrate..
how does one avoid ‘over use’ of lip to lip compression on any high note?
practice endurance of lower notes than the point of your excess..
so…if…
your high c has too much compression – become exceptional at playing ad nauseum between mid ‘c’ / ‘g’ on top of stave / and ‘a’ above the stave…
then—as a by product—- high b and c will be easy…
you probably don’t have a problem
its just your brain wants to write cheques your chops cannot cash
YOU AIN’T STRONG ENOUGH ON LOWER NOTES!!! 
I see this all the time..
its only when players stand next to me playing
do they realise how un-strong WEAK (endurance) they are ON THE STAVE
playing thru an arban study is EASY…
if its not EASY for you..
YOU ARE NOT STRONG ENOUGH !
the attached melody should be SIMPLE…if you cant get to the end easily…you are not strong enough!!
see pencil exercise pic—I can hold it like this for 4 mins….can you?
regards . .Roddy o-iii<O
roddytrumpet 