I read this from time to time and question the concept. If I analyse the process, it normally involves raising the tongue creating more of an "eeh" syllable instead of a "ooh". We use the garden hose analogy - put your thumb over the end of the hose and the water sprays farther. While it is true that the water does travel farther, the stream is much "thinner", and that is NOT what I hear from world class players using this "technique". So what is happening? Our tongue is NOT a thumb covering the garden hose, our lips have that function and they compress to play higher notes. When we compress the lips, we need more "air pressure" to blow them apart (not velocity or speed) but our breathing doesn't change so the additional pressure does not come from there. I found the answer in a horn loudspeaker developers course. Our mouth is a chamber between the pump (breathing apparatus) and embouchure. That oral volume is greatest when we articulate with a "Tooh" as the tongue is low in the mouth, the cavity above and below the tongue is added together. That cavity introduces an inefficiency which would lower the pressure that the lips see. The cheeks are also elastic when relaxed additionally making the chamber "softer". When we raise the tongue, we at least partially seal off the lower part of that cavity (between the sides of the tongue and the teeth), decrease the size of the upper cavity providing a more efficient path for the air to flow. That increase in efficiency is in air pressure not velocity and not "thinner". THAT is what I hear when listening to world class players. Paul Klipsch published several papers on his design of the Klipschorn. The woofer part of the horn uses a chamber right in front of the speaker to modify its response. Trumpet players have a variable chamber. If you are still sceptical, let's finish the garden hose analogy: the pump is our breathing, the hose our throat, I'll let the thumb be the tongue and we spray the water into a bucket with a hole in the bottom (our mouthpiece). I can spray fast water into the bucket, what drips out of the bottom has NOTHING to do with that spray speed. We can add another level of complication, we seal the hose and the bucket off at the top (like our lips and the mouthpiece rim). We spray fast water into the bucket, it still only drips out until the bucket is full and then the bucket of water starts fighting back - the hole at the bottom of the bucket (the mouthpiece throat) is the determining factor here, our spray velocity has been neutralized by the entire system. If the hole in the bucket is the same size as the hose diameter, water will pour out at the same speed as the open hose! With a trumpet, we have a much more complicated situation as the air doesn't really pass through the horn like that leaky bucket. The resonance of the horn also "fights" back further limiting velocity, but increasing "pressure" which aids the upper register. For all of you that were helped by the speed visualization, essentially you were not told the truth, but the end product - better upper register was the same. Maybe with this post we can start telling the truth and wonders of efficiency instead of the myth of velocity. Any additions or corrections are appreciated!!!!!! This would make an excellent theme for a doctorate! Any takers? I have further insite here, let's get some responses first!