I recently had some problems with my tone quality. My tone was really airy and anytime I tried to hold a note the pitch would go all over the place and I could not hold it steady. I don't know if you're having those kind of problems or not, but if you are try leadpipe buzzing. Pull out the tuning slide and use your mouthpiece to play on the leadpipe. The goal is to get the pitch to where it sounds the best (the least airy) and hold it there. After you achieve that and do it multiple times try slurring up to the next note which is around a 9th plus a half and try to steady the pitch up there. I've done that everyday for a week and my tone quality has greatly improved.