OK.... I think I understand that what you are saying is that the size of the oral cavity affects the speed of air through the cavity and thus the frequency produced. When you read the article on resonant intonation you gain the concept that the size of the oral cavity also affects the natural resonance within the oral cavity. In other words, the vibration that is feeding back from the air column within the horn "focuses" through the opening of the embouchure and can then create some harmonic resonance INSIDE the oral cavity that also helps reinforce the overall vibration of the system (the "system" consisting of your oral cavity, the embouchure, the mouthpiece internals, AND the horn itself). (the oral cavity kind of works like the resonating "bulb" on the back end of some stringed instruments). For a crude demonstration of this, open your jaws and hold them at a fixed distance apart while tapping your cheek with a pencil while adjusting the position of your tongue. You will get a different "frequency" of "pop". Why should this happen?...there is no air moving so velocity is not a component. I think that "Yes", you are achieving different air speeds against the embouchure by moving your tongue around... but you are also varying the angle of attack of air against the embouchure AS WELL AS changing the natural frequency of the oral cavity by adjusting it's volume and that all of these have an effect on the natural frequency that "the system" vibrates at. Anyway.... cool discussion. Thanks. I reckon at the end of the day we just do what works without getting overly bound up in the physics involved or we'd suffer "paralysis by analysis"! That leaves us to concentrate on the MUSIC.