So the best way to explain embouchure is as a way to place your mouth around the mouthpiece and the reed to enable the most free vibration of the reed. It's essentially the reed vibrating is what makes the sound on the saxophone. The best starting point for a single embouchure is teeth on top of the mouthpiece, and the bottom of your mouth not really biting against your lip, but a bit of lip between the teeth and the reed, like that. Should be set just around where the reed departs from the mouthpiece. That's probably the best place to place your embouchure.
A little over that and you're going to be sounding a bit brash, and a little behind that, you're going to sound muffled. The best way to explain a single embouchure is to start with the teeth on the mouthpiece, like that. And underneath, you want to have a little bit of lip over your teeth. Not that you're going to be biting up against it, but you're going to be placing some pressure on the reed. The best place to put this is as I said just where the reed departs the mouthpiece.
You don't want to be using any unnecessary muscles around your mouth. You want to be as relaxed as possible. If you look in the mirror and you look like the son of Frankenstein, something's wrong, okay? You're going to be restricting the reed and closing off the mouthpiece, which is going to sound choked. So you want to be as free as possible with the mouthpiece and the reed.
A little too far in on the mouthpiece, you're going to sound harsh. Not too far enough, you're going to sound muffled. Okay? The other thing is you don't want to have too much extra bunching in all these muscles coming up. See how that sounds restricted? And for the second time you don't want to be pushing your chin down too far, because that's going to sound harsh.
You have to find a natural balance. You don't want to be like this. And you don't want to be like this. You just want to be like this. Just like you're closing your mouth. That's probably the best way to explain embouchure for the alto saxophone.