I was playing exercise 22 in the H.L Clarke book yesterday and I felt a slight increase in mouthpiece pressure as I scaled up to high A (the one just above the staff). The resulting high note sounded airy around my second repeat of the exercise. I understand that some mouthpiece pressure is needed as one ascends to higher registers, but exactly how much is enough? Should I possibly consider learning how to buzz into the mouthpiece? From what I read on a number of sites regarding it, mouthpiece buzzing is an ideal way of minimizing pressure on the mouthpiece, however there is much debate on its effectiveness.