I never thought about fully relaxing my tongue until after I read this post, which was on another messageboard. You can find it through googling (relaxation is passive trumpet), but otherwise, the mind-changing post (shortened, of course) follows: "I can't believe how all this bad advice keeps circulating about an "Open Throat". If you try to do the same action as yawning while you play you will be putting a lot of unproductive energy into your playing and just adding a different kind of tension. The best thing to do is to only "relax" the throat. Relaxing is passive, that is, a complete absence of muscular action. Any muscular effort to try to force open the throat such as yawning action, dropping the jaw etc. will do nothing to improve the sound...The quality of sound is defined almost solely by the ability of the embouchure to vibrate at various frequencies. All that is required is to apply air flow...Of course the volume of the sound is a function of the air velocity. An efficient vibration point will also yield greater volume for a given velocity of air... It kills me how all these students and teachers talk about is air, how to use more, how to create more abdominal pressure and all that, as if that is what defines and creates the sound. It does not. Fact: Air flow and the pressure behind it only provide the power for the sound. It does not provide any tone color or any effect to the frequency content of that sound..." If you google the above mentioned phrase, you'll find it. The guy, in summary, said that to open the throat, you need to relax. Opening the throat through yawning just "moves" the tension. Air only provides "power," while the vibrating lips provide the note. (He later went into an example that compared an amp, voice coil, and speaker cone to your lungs, embouchure, and trumpet.) Some of this stuff was really new to me, in that I had never thought about it. I mean, I knew that faster vibrations were key, but not that you had to relax and not yawn to open up. What this guy says is true. When I really focused on relaxing my tongue, my sound opened up, although flattened somewhat (due to the embouchure), and the pressure that was always present disappeared. Before I tried fully relaxing my tongue, I would always feel pressure when playing, and the back of my tongue would feel warm and uncomfortable as I breathed when not playing. However, I relax easier when I'm lying down. Any tips on how to relax when not lying down? How I should I hold my jaw? When I'm not focusing, my tongue will creep back up into that same uncomfortable position when I breathe or play. Sometimes, the discomfort won't go away (if I can't relax) unless I physically push my tongue down with two fingers (like now).