After more than 14 years of trumpet playing as an amateur, I have incirporated in my playing something that changed my high register ability and also my flexibility. I am shure that most of you know about the Donald S. Reinhardt/David Wilken 's ''pivot'' system. Yes, I know it isn't really a pivot, but just so to speak ... I found that I am a ... let's see... I think a IIIB. So I've descovered that I have to pull down together to ascend and to pull up togheter to descend and a bit to the left in both cases as my central incisives are crooked uneven. This made my upper register much, much easier as well as my lower notes below the staff. Also, when in the upper register, I think of blowing up in the upper part of the cup in the mouthpiece, and when in the lower notes, I blow lower. I know this might not be the actual things going on in there but I use this as it works wonders when playing.
Today I had a brassband rehearsal ... not a long one but almost 1 hour... and in the end I was able to play a high F after some up-an-octave measures. I have also practiced and fooled around for about 30 min before that rehearsal . I am now playing on a GR 65C*#2bb wich isn't a ''cheater mouthpiece'' and I am very pleased with this.
I know that this might be true for me in particular only, but maybe someone will find this information helpful in their playing.