- Fens of Lincolnshire
My first sax teacher tried to encourage me to "drop" my jaw when playing the lowest notes, which is similar on trumpet too. Unless there is a slight technical problem it is possible that it is about tight embouchure. It is perfectly possible to play notes an octave above your fingering by tightening your embouchure.
Yes, I think you are right. The lower D I struggle with, but it gets better going higher (ie E, F etc). Having come from a clarinet, I need to relax my embouchure more. My tutor said that would be a problem to start with. Maybe I am blowing too hard as well?