Re: Re: Re: Re: Re: Low register dynamics


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Posted by Rick Denney on February 13, 2004 at 11:28:21:

In Reply to: Re: Re: Re: Re: Low register dynamics posted by Air VOLUME on February 12, 2004 at 20:09:42:

Okay, guys, you are talking past each other.

With a given aperture (say, the throat of the mouthpiece), and on the simplifying assumption of an incompressible fluid, flow equals aperture area times speed (this is the basic Q=VA equation in any fluid mechanics text). Thus, increasing speed increases flow, because the aperture is constant. In that sense you are both right.

Now, to pressure. Stick with me here, because I think this is the critical issue. If we remove that simplifying assumption that the fluid is incompressible, then pressure comes into play. What makes the pressure higher? Holding the lips more tightly together, which affects the force required to part them and also the size of the aperture when they part. The pressure of the air inside the mouth forces the lips apart, and that pressure is released sending a pulse into the mouthpiece. The pressure drops suddenly, allowing the lips to close. The closed lips allow pressure to build again. We control both the force required to part the lips and the air that will apply that force. (When we apply this to a specific frequency, we quantify the work we have to do to create a certain pitch using the term impedance.)

Generally, the tighter we hold our lips, the higher the pressure has to be before the lips will part. If we hold our lips and teeth a certain way, we can create high pressure without increasing the resonant frequency of the embouchure, which allows us to play a given note with higher pressure. Higher pressure will do the work on the lips more readily, so we don't need as much flow. The problem is that the sound pulse is weak if the pressure is not backed up with a good volume of air. This gives us a thin sound in the low register. We often build the pressure while keeping our lips relaxed enough to make a low note by closing the aperture behind the lips--we play through clenched or nearly clenched teeth. This is the big no-no everyone is trying to prevent when they talk about warm air and volume vs. speed.

Here's the breakthrough concept for me: We can also force the lips to part with the same overall force by applying a lower pressure to a larger lip surface area. To do that, we have to expose more of the inside of our lips to the inside of our mouth where the air is, instead of hiding it with our teeth and tongue. This means opening up the aperture between our teeth. This is accomplished by lowering the jaw, and even by letting the lips curl out. Pressure goes down, volume goes up, speed goes up. This is how you play loud and low. (With a strong embouchure, you can also play with that open aperture in the upper register, which is what Jay Bertolet means when he favors using a single embouchure "set" for all ranges. Tone benefits, but the chops have to be able to control all the pressure needed to produce high frequencies.)

The problem people run into in these arguments is that they equate pressure and speed. They are different things and don't always track alongside each other, especially in the low register.

So, when people talk about using warmer air and increasing volume, they mean lowering pressure. This is done by exposing more lip surface to the airstream, by dropping the jaw and letting the lips curl out. You can still tighten the aperture slightly without changing the volume of air, which will increase the speed and pressure a little. This will raise the pitch, but that's a different mechanism. When people talk about playing louder using more speed, they don't mean more pressure, and they don't mean closing the teeth and tongue to create the feeling of more speed behind the embouchure.

Rick "who can describe it but who can't yet do it" Denney


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