I play on an old Selmer Low C bass clarinet that my school owns. The instrument plays pretty well in all ranges except for just above the break. The range from B to the D just above the break is really resistant and hard to play in, especially with regards to dynamic control and tone quality. However, the moment I switch to notes below the break (throat Bb and lower) or higher than the D (E on the top of staff to higher notes) the instrument plays beautifully. I can't figure out why this is. Everything seems to seal and open properly. Has anyone else ever encountered this problem before or has a clue as to how to fix it? Thanks!