A few days ago I got a new Stomvi Old Style 3C mouthpiece. I absolutely adore my tone and have had successful results with this mouthpiece. However there is one problem - my ability in the higher register has decreased significantly (I used to be able to comfortable do a double octave C scale, now I struggle to hit those kinds of notes). How to increase the middle of my range? What things can I do to really get my ability back up to hit those higher notes beautifully with this mouthpiece?
I'm Grade 7 (Australia) and I'm going into Grade 8 next year (the highest, except for the masters' exams A-MUS and L-MUS). My exam is in 2 months or so. I can do everything I need to well, but I would like to increase my range to make sure I can comfortably play the higher notes.
I also find that certain warm-ups can absolutely wreck any possibility I have to play higher notes, where as some facilitate them. My warm-up routine has a good balance between high note working and low note working (and of course, middle range working). They are basically lip slur arpeggios going up and down. Anything else I could incorporate to improve my range?