From my experience in the amateur musician’s circuit, every musician and instrument combination has a “nemesis note” or two. Sometimes it really is the instrument. But it’s my opinion that a nemesis note is usually one that hasn’t found its centre yet.
Every note has a sweet spot in terms of embouchure. For me, the upper range is usually better (clear and singing) when my embouchure is in the centre of the mouthpiece. And the low range used to be better with the mouthpiece sitting on the right side of my lips. That made for difficulties in quick passage crossing from low to high or with slurs over large intervals. Can you picture me sliding across the mouthpiece as I cross over Bb at the bottom of the staff? What a pain and waste of energy. I had to fix that for sure.
So I’ve mostly corrected this. A consistent embouchure over most of my range makes for consistent tone quality as I move up and down. But there are still the nemesis notes…
I’m trying to make up time on my C tuba so I’m feeling some pain with Db/C#. After an hour or so on Db major scale studies, I finally felt I could make a really nice clean and quality attack on that note. Consequently, D and Eb felt better too. I feel that if I can hit the note at ffff (quadruple forte) with a ‘nice’ snappy and brassy attack then the attack at mezzo forte will be clean with no fluffy edges. That’s been my method: expanding the outer edges of my dynamics means articulation in the normal range will be quality stuff. Crazy-loud attacks under some reasonable control means that regular old double forte will be performance-worthy.
Back on the subject of centering notes… Here’s what you do: take a nice deep breath and start a long tone on a note you’re not happy with. Then, without breaking or changing notes, move your lips around. Slide around the mouthpiece a little. It’s good to have a tuner listening too. Move around and experiment until you get the best of both worlds: clear open sound and the pitch is in tune. You should do this for all but your best notes. Practice consistently and remember your embouchure for these notes and make use of it in everything from scales to studies and repertoire.