When playing the trumpet many players actually use too little air. It is necessary to strike a balance among air volume, air speed, sound volume, tone, and range. This is done by controlling the amount of air you supply at the lip aperture and by controlling the size of the aperture. Playing low requires a more relaxed aperture with a relatively large volume of slow air. As you go higher you need to increase the air speed, reduce the aperture (to reduce the vibrating area of the lips), and increase the speed or the air. I think many players simply close down the aperture which reduces the volume of air flowing. I believe that, in order to make playing the higher notes easier, you must increase both the volume and speed of the air in order to support the embouchure properly. If the embouchure is not supported properly, you will start to make accodations in your playing to be able to play the notes. Then, the embouchure is not in control. Playing higher should give a feeling of control similar to that felt in the mid register (in the staff). For example, I think many people (myself included sometimes) have a tendency to close off the throat when not providing the proper support. If you start using more air, your embouchure does not have to be as small which means that you don't have to use quite as much air pressure (which can give you those head rushes when you play high). Air speed is controlled by the volume of air being pushed through the aperture and the aperture size. The smaller the aperture, the higher the air speed. So, use more air and in order for it all to get through the opening, it has to go faster. Analogy with a garden hose works for me. If you turn on the water just a little it will almost fall out of the end of the hose. If you then increase the volume of water coming out (open the valve more), it will squirt out farther. In other words it has more energy. If you close down the aperture with a small flow, it will squirt out a little ways. If you close it down with a larger flow, it will squirt out much father. For the same opening size, the water has to move faster to get through the opening if the volume is high. Without sufficient air volume, the aperture has to be small to obtain sufficient air velocity. This leads to a weak sound since less of the lips are vibrating. I like to start at about the top of the staff increasing the volume of air. When you do this, you can use a slightly larger aperture for each increasingly higher note than you would use if using less air. Opening the aperture keeps the tone and volume down (doesn't let the tone go to the next partial while playing softer). Increase the air even more as you go up. Now, instead of reaching a very small aperture size at lower notes, you get to that size at higher notes. The upshot is that you still have adjustment room in your embouchure for the higher notes. If you don't provide enough air, you will reach a point where it is very difficult to get higher notes because you have already got your aperture very tight before you get there. The result can be either a buildup of too much air pressure (Head Rush time), use of mpc pressure, and/or closing off of the throat in an attempt to play the high notes. Closing off the throat is (I think) an attempt to increase the air speed by trying to make the throat smaller than the embouchure. I don't think this is possible and for me, the result is a very weak tone lots of pressure. This whole concept of using your tongue level to change air speed is very cumbersome for me. I don't see how it is possible to increase air speed when the aperture at the lips is a smaller aperture. The air speed is controlled by the smallest aperture in the system which is the lips in this case. If you increase air speed and then send it into a chamber (the rest of the oral cavity) that is larger, the speed decreases. Then at the lips, it increases again. I think the tongue level thing has more to do with resonance and the resistance that we feel when we are off resonance. (Just MHO).