I'm new here, so bare with me. I've been playing trumpet now for about three years, started in the sixth grade. Anyway, just recently I've been having problems. For some reason after playing for a while, usually just a couple songs, my tone starts sound flat and my playing sounds muffled. I don't know what to do, it just started happening all of a sudden. Has anyone had this problem, and could you help me if you know what's wrong?