Right ... Em-bouch-ure is easy to remember if you know French "bouche" (mouth) ... as in "Fermez la bouche!" I usually hear AAHM-boo-shure or AAHM-buh-shure in Anglay, among us latte drinking whistlers.
In my experience, the generalization is that whistles with larger (taller/wider) windways and/or wider beaks tend to respond more dramatically to embouchure tricks. That includes most low whistles, of course. Also Susatos and Copelands, among others. Generation type whistles seem least sensitive.
The key dimensions of whistle embouchure are:
o Depth
o Angle
o Elevation
o Aperture
o Shape
Depth: How much of the beak you take into your mouth. From just touching the tip of the whistle to your lips, to "eating" a good deal of the beak. A shallow embouchure allows more angle and aperture control. With a deep embouchure, your upper lip tends to act as an air dam above the fipple window, and may strengthen the tone, particularly toward the bottom range. For example, this effect is noticeable on the Copeland D.
Angle: This is the famous "playing sideways" thing. Beyond looking cool, it narrows the effective aperture and directs the airstream against the side of the windway, resulting in a breathier tone. This is particularly effective with Susatos for taming what is often criticized as a too-loud and/or too recorder-like tone. Works best with a shallow embouchure, the whistle just against the lips.
Elevation: The angle of the whistle relative to the body, from pointing toward the floor to pointing straight out. A downward position narrows aperture, and directs air toward to top of the windway. My Overton low D is sensitive to this, benefiting from a low elevation in the low register, and a straighter approach as you move up the range.
Aperture: The tightness of the lips, allowing control of the relative air pressure vs. air volume going into the instrument. Requires a shallow depth. Particularly useful for taming the upper notes of a shrill whistle, and can also be a side-effect of angle and elevation, as mentioned above.
Shape: The shape of the mouth cavity and the position of the tongue within the mouth, from a large "aaah" to a narrower "eeee" shape. I'm less convinced that this has a discernible effect on the tone perceived by the listener. But subjectively, the resonance of some whistles seem to come alive with a larger shape. And shape affects the movements of tonguing within the mouth. Of course, for circular breathing, the continual control of the mouth air chamber is essential.
I agree that obsessing about whistle embouchure is silly. It's far less critical than other fundamentals of breath control and fingering technique. But not much different from fiddlers thinking about bow tilt, or guitar players thinking about pick angle. It's fun and easy to experiment with, and might lead to interesting discoveries about the latent possibities of a given whistle.
