Most of you who have worked with me have probably heard me say BREATH SUPPORT so many times that you don't want to hear it again. Breath support being the most important component of a good clarinet sound, it's no wonder that I harp on it.
I don't think I've talked about embouchure very much, mainly because it's the most important part of clarinet tone, but I've had two people come to me in the last few weeks complaining either that they play sharp or their chops get really tired after a short time playing.
Yes, I talk about breath support first, then embouchure. The way I coach for clarinet sound is to try to develop breath support first, then we work on the embouchure, especially the position of the clarinet and the relationship between the mouthpiece and the embouchure (how much mouthpiece to take in, what angle to hold the clarinet at, and the use of the upper and lower lips).
Generally, once a person gets this stuff down, they naturally (and unconsciously) adjust the tension of the embouchure to create the best sound. However, when I'm coaching "on the fly", I rarely get past breath support and basic embouchure concepts. Unfortunately, most of the people who come to me with a particular problem don't spend enough time with me (and in the practice room) to understand and develop breath support and embouchure; they want a quick fix.
I don't like "quick fixes" because they're never really quick, so I don't dole them out. However, here is one technique to diagnose pinching that will usually fix playing sharp or embouchure fatigue.
Take the mouthpiece off of the clarinet.
Turn your tuner on.
Play the mouthpiece alone.
The pitch you should hear is the D above the staff (concert C).
If the pitch is sharp, you're pinching.
If the pitch is flat, your embouchure is too loose.
Practice playing just the mouthpiece until you make the feel of what you're doing a habit.
Important! You don't need to get the D spot on on your tuner, just close.
Over and out.