Can you expand a bit on this, Dr Mark? In my youth I had range to high E with good tone but excessive mouthpiece pressure, which I've being trying to get shot of on this current comeback. Just now I have a strong open aperture range low down, and an improving high range from high Ab upwards. But a weak pivot/aperture compression/tongue arch transition phase between D# and G. These notes are difficult to hit and take a lot of air just to get any buzz at all. I'm sort of hoping that with practise it'll all just blend in eventually, but..... Any reassurance/advice?