DirtyErnie wrote: Hurts like a b#@%h at first, but is definately worth it. DON'T TENSE UP, just let it happen.
Well, Ern, borrowed or not, it seems oxymoronic. If it "Hurts like a b#@%h" I don't see how you could possibly not be in the tense state that you say to avoid.
MA, who says "look up oxymoronic if you don't know what it means"
Your question made me think about my own horn and back when I was trying to figure out what was wrong with my middle C. It plays very well in tune with itself most of the time but has a somewhat quirky middle C. I could sing it easily, and would check my buzz and find it to be right on but would sometimes miss it on the horn. It would come out sharp or want to frack. The D above it was solid, as was the Bb or the B, but middle C gave me fits. I learned to power through it, but later I found that on my particular BBb horn, the fourth valve just works better.
One thing I sometimes tell my students (but this is always on a case per case basis, but usually does the trick) is to make sure the airstream moves downward for high notes.