When I first got my cornet I did not note any differences. Then, gradually, I found that after about 10-15 minutes of playing my lips were shot. Could not even play a tuning note, just sputtering air. Picked up the trumpet, played with that, no problem. Eventually I could play some more on the cornet, but not a full session.
I am using a 6B in my trumpet, same in cornet. I have tried a 3C and a few others, but I seem to get the same results. Is this normal, any simple answer, or??