Hi All, This is my first post on here. I have searched for my specific question in other threads and couldn't find it, but I apologize if this has already been discussed. I play on a Kanstul 1600 with a GR 64SZ mp. For probably a year or so I have been "stuck" at a G above high C. No matter how easy the G gets I cannot produce an A that feels solid and real. That was the case until recently when I just happened to try playing the A with the 3rd valve - it came out as clear and full as any other note I play. What's going on here? Is it a reflection of my technique, my horn, my mp, or some combination of it all? I'd like to learn more about this as sometimes I feel like I'm doing everything correctly and have never been able to play the illusive double C. I've talked to several players who use alternate fingerings for tuning purposes but have not encountered anyone who could ONLY play to a certain range by way of alternate fingerings. Any stories or advice? Thanks.