I’ve been playing Tenor for about 6 months, and I’ve noticed that my high notes; such as, High E to High F# are thin sounding. [No altissimo notes yet]. Johnny’s high notes sound full and robust. They actually sound as full or fuller than my middle register notes. I’ve tried different reeds and mouthpieces. The mouthpieces sported different chamber sizes, etc…but with one constant: the tip opening. All the mouthpieces had around 7* tip openings as it would relate to an Otto Link.
Will going to a larger tip opening enable me to fatten up the high notes? Or is this something that has to come with time and effort?
Without hearing you it’s difficult to say. I think a #7 should be open enough. My “guess” or suspicion would be your air supply. As we move up the horn it needs more air than the middle range otherwise it will sound as you say, thinner.
Try playing reasonably loud and as you get close to that high range increase the amount of air from down low in your diaphragm. Go as extreme as you can without breaking the notes of course and see if this starts to help.