Firstly, thank you for the great site.
I have few questions about embouchure.First, I am in a high school band, and one of my senior, can produce a very beautiful tone using RC,which is the same as ours. And when he plays, I can hear that some air was coming out from his lips, which means he did not seal his lips firmly, is this the reason why he can produce a good tone? And the second question is that does the great clarinetists also use the standard embouchures?
First, the air escaping from the sides of the mouth of the player has nothing at all to do with their tone, nor their embouchure. In most cases air escaping from the sides of the mouth can be fixed with concentration on keeping closed, so-to-speak, or simply disallowing the air from escaping. It takes some consistent work which is not terribly difficult. It can distract the listener from the tone of the player and once in a great while can hold the player back from advancing.
As to your second question, the clarinet is played with the same embouchure except when the player uses what is known as “double-lip”, in which both lips are placed over the teeth. This is the more natural of the two embouchures and can produce a lovely sound. However most clarinetists play with what is known as “single-lip”, wherein the lower lip is placed or stretched over the teeth. An equally lovely sound can be produced here as well.
There are other apsects of embouchure, however excellent clarinetists are also gifted with an excellent “ear” and sense of time, which is somewhat indefinable. There is also an almost obsessive desire to achieve excellence, and even then, it is somewhat fleeting, or can be.
I hope this helps.
best of good luck.