Hey all I've a question,
What exactly does your jaw do when you are playing? Is it tight, loose, does it change? Being pretty much self taught to start with, I've realised that I'm using my jaw to almost clamp my lips together to get higher and lower with very little tensing of my lips. Obviously this isnt the way forward but I'm finding it very hard to unlearn.
Any advice?
Thanks
Chris

umm.. try buzzing without the mouth peice - then with the mouthpeice then with your instrument... try long notes - make sure you're not pressing - and make sure your bottom lip isnt tucking under- this will affect your tone

are you biting your lips together (if you are DONT!!!) you should have your lips in fron of your teeth and use the mucles in your face to tighten your lips to get higer notes - and even tighter to get lower notes. - this take a lot of practice and it will take you weeks to notice the difference in tone and note quality.

Thanks for the reply, its not like im literally biting my lips together but more like the position of my jaw changes along with the pitch, a few days ago i could only slur arpeggios by moving my jaw up and down. I can hit top C's with very little pressure (ive rested the instrument on a table and played without pushing it along)
Its just im a bit concerned that I'm getting into some sort of bad habit, I dont have a lesson for another 8 days and thats a lot of practise time to be doing something wrong!

On the horn it's normal to move the lower jaw to some extent. However, it's not up and down, but forward and backward. My teacher told me to aim the airstream horizontally into the mouthpiece for low notes and downward towards it's lower surface for high ones. What I think happens is that taking what pressure there is on the lower lip leaves the upper one (which does most or all of the vibration that produces the sound) free to oscillate slowly, while transferring the pressure to the upper lip reduces its freedom and helps it to oscillate quicker. Horn players are expected to have a range of at least three and a half octaves, and trumpet players are usually considered adequate with less than three, so I would expect the trumpet to need rather less jaw movement.

Most people would be very pleased with a low pressure top C. If it has a good sound, you must be doing something right.

I used to place (approximately) 1cm cubes between my back molar teeth when I played, advice from my brass teacher as he reckoned you teeth should be no closer than this. Although I don't do it any more, it's quite a strange feeling (hard to swallow) and there was always the worry I might swallow the cubes themselves

I remember my cornet teacher saying something similar about moving the jaw back to pull the bottom lip slightly under which changes the direction of the air and puts more pressure on the upper lip.
On the cornet I could never get any higher than an A above the stave, no matter what I did or how I did it. Since picking up a horn it just feels so less restrictive when hitting notes that are right up there. Overall my mid range is fine, when I get to about a G above the stave I start tensing up and I feel my tone suffers if I try to play too loudly. I can reach as low as the G at the bottom of the bass cleff but theres a grey area between that and the G above - I cant fight the urge to purse my lips rather than open them which makes pitching really difficult!

My low to middle register used to be very weak. My third teacher (1994) sorted that out. He checked how the bottom of the mouthpiece related to my lower lip and teeth. He told me that for the register from middle C down to C space, the mouthpiece should sit near the top of the teeth, with the lower lip acting as a sort of pad, slightly compressed. Once he had made that change, one or two low-register studies per lesson produced a marked improvement, though I'm still not a natural 2nd and 4th player.

Ok all my problems have been solved. It turns out the mouthpiece Ive been using has a strangely shaped bore. After finding a standard one at the band hall and giving it a go everything has become so much easier!