To play the high notes on the saxophone can sometimes be like walking on quicksand. A fingering that is nice and smooth in the middle range gives you squeaks and splats in the high range, or sometimes just falls an octave. This is because the higher notes are more about airspeed and mouth cavity than about fingering. So rather than using more embouchure pressure to “force” the pitch, try to create more of a concentrated airstream and keep the back of the throat open, like an oo or ee sound.
Some students will lift the chin up or clench the jaw in order to get the sound to pop. This can cause the muscles to get too tight, which will result in the reed stopping the vibration. Instead, tighten the muscles in the mouth at the corners of the mouth, but try to keep the center of the mouth as loose as possible. Try to keep a straw in your mouth without squishing it. Also, try to support your air with your stomach muscles and not from your jaw muscles. You should feel the note pop up clearly without clenched muscles.
I often hear people just going directly up to the higher pitch without setting up the embouchure. It’s more like a balance sort of thing instead of a heavy lift. So, try going from the middle note, try sliding from the middle note up to the higher note without tonguing, and listen for the place where the pitch wants to break. And if it breaks, just go right back down and get your air going and try again. It will teach you to come up to the upper register instead of just banging into it.
With a consistent daily routine, however, this range can become much more dependable. Begin by spending a couple of minutes sustaining middle range tones with a full, steady sound. Then play a middle range note and the note above it, alternating between the two while sustaining each one for a few seconds. Play in a moderate volume. Blaring away will allow you to feel like the issues are being worked out, but it will most likely only cover up the problems. After a few attempts at this exercise, try playing a short scale that includes the upper notes you’ve been working on. Use the same ease of support you used during the exercise. Fifteen minutes of practice like this will help you develop the necessary co-ordination without straining your embouchure.
If your high range is still a bit shaky, make sure it’s not a physical issue before deciding it’s a technical one. If your reed is too soft, it will close when you push air through it. If it’s too hard, it may not vibrate at all. Reed placement on the mouthpiece is also an issue. Taking a little more mouthpiece into the embouchure can help with high notes because it gives the reed space to vibrate. Constantly monitoring your air and embouchure will help your high range slowly become less of a crapshoot and more like the mid-range of your clarinet.