You should probably practice your concert music also. Whether you play trombone or saxophone you should almost always have a seal where your lips meet the mouthpiece. Puffing out the cheeks ,although not reommended by most music teachers, shouldn't make a difference. In fact I DO teach puffing out the cheeks to my advance students as it is needed for advance techniques.
What should you do? As much as everyone is often looking for a quick fix there really isn't one. Your lip muscles and surounding muscles react and work mased on what e call muscle memory. Since the muscles themselves don't have a brain it takes them awhile to learn what they are supposed to do. You obviously have been teaching them to let air out around th mouthpiece. You need to retrain them to not let air out from around the mouthpiece. Very slowly play some soft easy long tones in your middle range concentrating on relaxing but still keep the air sealed in. The do some slow scales, then do some of your music. You can slowly speed up but once you notice air escaping STOP and go back one metronome makring and try again, increasing your speed, range, and volume slowly.
If you do this correctly and patiently you shouldbe playing properly in about 4 days.
Re: Crisis Situation 18:00 on Saturday, March 27, 2010
I found that wetting my lips a little by licking them helps me to make a better seal around the mouthpieces when my mouth is too dry.
You might also find that the reeds you are using are forcing you to blow much harder than other reeds.
Also if you are young then maybe your face muscles have not toughened up yet. I found that practicing trumpet toned my face muscles immensely & made blowing the sax 10 times easier.
Dizzy Gillespie who is possibly the best trumpet player of all time puffed his cheeks out like a bullfrog, so there is no shame in that. It can also help create a different embouchure effect & thereby create a different & perhaps better sound for you. The main thing though is to try & seal your lips around the mouthpiece so that you don't waste air pressure. Rico Royal reeds are easy to blow & produce a high quality sound. Maybe try a size 2 or 1 + 1/2 & you'll find you don't need to blow half as hard as some of the other reeds. I'm using Rico Royals size 3 + 1/2 at the moment on my tenor sax & they are far easier to blow than the Vandoren 3 + 1/2, & they produce a wonderful sound.