I just returned a few days ago from a 2 week music camp at the college that I'll be attending in the fall. The professor who taught my clarinet masterclass will be my clarinet instructor for the next four years. Anyway, one of the seemingly simple things she told us the would improve our sound is to simply take in more mouthpiece (she gave us a guideline of just how much). Upon testing this, I've realized that I only take in about half the mouthpiece that I should. Now that I've been trying to use more, I tire more quickly, squeak horribly, and can barely get into the altissimo register. I realize that this isn't something that I'll adjust to overnight, but I feel like I can barely play at all right now. I know what my embouchure is supposed to look like, but I guess I'm just not sure how to approach fixing it. I'm almost tempted to wait until the fall (only about 4 weeks till I start classes). Right now I have to practice for auditions and feel like I can't afford changing something so big. Another thing that I'm wondering about is how the mouthpiece itself affects embouchure. Right now I play on a Vandoren B45, but I feel like it's probably not the best mouthpiece for me. I do have a pretty small mouth (I'm a very small person) and know that some mouthpieces are smaller and probably better suited to me. The professor and I did discuss looking for a new mouthpiece for me in the fall, so I'm also thinking that this might be another reason for me to wait to change things.

I know I kind of rambled, but I've been really frustrated with my playing the past few days. I'll probably be meeting with my current clarinet teacher three more times before starting school and switching to this new teacher. I kind of feel like I'm in a transition stage, so any advice anyone has to offer would be appreciated!

I think that not taking in enough mouthpiece is a pretty common problem, but one worth sorting out. I wouldn't worry too much about the size of your mouth - mine was far too small for all of my teeth before the nasty dentist removed a few of them. My backup mouthpiece is a B45. I'd spend some time getting to grips with developing a better embouchure before changing mouthpiece so you can make a more informed choice.

What reed strength are you using? A B45 doesn't need a particularly hard reed.

The other thing that might help is to slightly increase the angle between the clarinet and your body.

I may have just written utter gibberish (had a long day at work and am typing after a glass of wine) I'm sure others will have more coherent thoughts.

You've written some good advice CJB, wine or no wine!

I'd experiment to see how much mouthpiece you need to take in - I have a feeling you've gone from one extreme to the other : while too little mouthpiece will give you a stifled sound with difficulty getting much about a clarion A, too much will make you a real squeak risk.

Apparently there's very good evidence to suggest that it takes 3 weeks of concerted effort to change a habit. A couple of years ago after a blinding revelation I made a fundamental change to my embouchure. It affected everything that was going on in my mouth, like you I was tiring more quickly, the top and bottom range were unstable and I had to make a big change to the way I was tonguing. During the time I made the change I focussed almost exclusively on playing long tones and scales (tongued) throughout the range of the instrument. I didn't practise for more than 30 minutes without a break and set myself a regime of 30 minutes practice, 2 hours rest, 30 minutes practice etc all day at weekends.

It took me about 2.5 weeks before the new embouchure settled but it was well worth the effort. Opened up my sound and gave me much more flexibility.

If I was in your shoes, since the advice came from your future tutor I'd do what I could to fix it before I saw her again, rather than have her think I'd ignored what she told me.