Quote:

The bass clarinet is a unique member of the clarinet family. If you don’t
voice it correctly in the upper register you’re in for a surprise, and
disappointment. One of the big problems playing the upper register is how
easy it is to get the high overtones. You think you’re squeaking but you’re
really playing the altissimo register. The bass clarinet has an incredible
range; the problem is how to control it. Try this for kicks. Play a Bb3 and
pinch or voice up a bit, you should get a G4, pinch more and you get a C5,
pinch more, it keeps going, and going and going. You’re not squeaking,
you’re playing overtones. You have to avoid voicing high or pinching in the
upper register or you’ll be higher than a kite. A bass clarinet squeak is when
you skip to a low note and it chirps, or you hit a throat tone key when you
shouldn’t. You’ll notice because everyone in the hall hears it too because it’s
so loud.