Bixel if you want to "visualize" the air speed by making the aperture smaller and increasing the air pressure then that belongs in the "mental tricks" column. This is a valid technique. If it works for you then great! But since you are also changing the variables of aperture size and air pressure you can not qualify this as some purely mechanical "explaination" that air velocity determines (or influences) pitch. That would be a faulty conclusion if you are indeed interested in the pure mechanics. Dont worry about it. No one will judge your playing by your ability to spout popular explainatins of "air speed = pitch" so don't waste your time with them. Playing is an art. You do know how YOU play because it is evident by the music. You will NEVER be able to determine the air velocity so don't be concerned. Thanks.