The embouchure is an essential part of creating a good tone; it's like a carefully crafted doorway that the air stream flows through. The embouchure has only one job, and it should feel the same all the time, and that job is to allow the airflow to act upon the clarinet so that the best possible quality of sound results. Keith Stein calls the clarinet embouchure a combination of "sets and draws," meaning that you set some muscles and pull on others. And David Pino writes that only one basic embouchure setting is needed for the entire range of the clarinet (assuming the reed is doing what it's supposed to.) The clarinet embouchure is so sensitive that the subtle, most minute change in the muscular structure can result in variations of tuning and color that the clarinet is producing.
Playing the clarinet is all about comfort. For most, standing is preferred during auditions - it is actually best if the player sits in a comfortable straight chair, which is to say that a normal chair with padding on the seat and the back would be perfect (best without any arms,) but a chair like a recliner would be unacceptable. The idea of being comfortable is so that the player relaxes, so that there is no extra tension anywhere in the body. Extra tension would start at the airflow, which would trickle down to the embouchure, which would give the player a bad sound, then the player would be confused as to why the clarinet is producing a worse sound, so with the sound the tonguing would be off, and finally the technique would go wrong as well. That just shows you how important relaxation is! Clarinets are cool but as long as you are relaxed and comfortable there is nothing to worry about
Before actually touching mouth to mouthpiece, it is best if the player does a preliminary exercise to further prove the point of how everything should feel the same. First, with the reed, mouthpiece, and ligature together, take the mouthpiece and hold it sideways to the light. Look to see where the reed and the mouthpiece touch; this is where your bottom lip will touch. Now stretch your bottom lip across your bottom teeth so that the red part of the lip is on top of the teeth. This should, in turn, make your chin "dimple." Though it does, keep your chin flat and pointing downward. This is one of the most important parts of the embouchure, since if you don't keep your chin flat, drool will run down your chin. Now instead of a mouthpiece, take your thumb and place it inside your mouth, and gently lay your top teeth down. You should not be biting your thumb, but the purpose of the top teeth is to merely hold the mouthpiece in place. Now exhale air as if you were to produce a good airflow, and gradually close your lips around your thumb, being sure that your chin is still flat, and your to teeth are lightly resting on your thumb. Close your lips around your thumb until all of the air stops leaking from your mouth. Take note of what this feels like, this is what it should always feel like when you are playing the clarinet. Your abdomen muscles have a constant pressure against them, you have a certain amount of speed that your air is moving (imagine that its moving, the pressure will feel the same,) your chin is flat, and your top teeth are just sitting there. Try this a couple of times, then try blowing faster air, you will find that you don't need any much more muscle in your lips to keep it from leaking.
Now take your mouthpiece and barrel joint assembled in your right hand, and take your left hand and place it over the bottom of the barrel, and do the same thing. After that take your left hand away from the barrel, and again, do the same thing.
This is a great exercise to help get an idea of what things should feel like. To create an embouchure this way is very unnatural for the human lip, so it will take a good deal of practice to concentrate on the airflow and embouchure at the same time, but that's okay - Rome wasn't built in a day, you know. These are issues that college students still have to address, and some instances the beginning college student doesn't know how to create a good airflow, or a good embouchure until his or her instructor teaches the player. Your teacher may have a different exercise he or she may want you to do, as stated in the introduction, these are guidelines, this will never take the place of individual instruction.
Besides the standard embouchure described above, a small number of clarinetists use a technique taught by Auguste Périer at the Paris Conservatory early in the 20th Century. Rather than resting the upper teeth on the mouthpiece, the upper lip is rolled over them in a manner similar to the lower.
This technique, which is more difficult to acquire than the standard one, requires slow, careful development of the musculature in the upper lip. A beginner should not try to use it more that five minutes during a practice session during the first couple of months. Otherwise, there is risk that the muscles will be damaged, making it impossible to employ this technique.
To compensate the difficulty learning the “double lip” technique, practitioners contend that it produces a fuller, sweeter sound. Famous clarinetists who have used double lip include Ralph McLean, Harold Wright, Kalmen Opperman and his students, who include many orchestral players including Steven Hartman and soloists including Richard Stoltzman.
The Big Misconception
A big misconception about the clarinet embouchure is that it should look like you're smiling. This is not true at all! The "smiling" exercise will allow air-leaks, will tire out the embouchure more quickly, and will create more tension on the reed, making a good clarinet sound harder to produce.
Holding the Clarinet
This section to this "subchapter" is in in its place because the author has decided that holding the clarinet has everything to do with how the face looks. The clarinet should be held at a thirty-five to forty degree angle. When assembled, the clarinet's bell should either be between the players knees, or a little closer than that. The idea is that you want the airflow to go through the clarinet as easily as possible, i.e. a straight line. If the clarinet is positioned too far up, then the air bounces back and forth between the reed and the mouthpiece before settling in at a straight line, and this squeezes the reed so that you can't produce a good sound (this problem is more common that holding the clarinet too closely.) Holding the clarinet too close makes the airflow bounce off the bore of the mouthpiece, and though its a little different from holding it too far away, it's just as ineffective. In some rare cases the clarinet may have to be held a little higher or lower than normal due to its players dental condition. Those with overbites tend to need the clarinet closer to them while those with under-bites tend to need the clarinet away from them, and from then on its just how the teeth are arranged.