Again, this is just an idea, but I think one of the big differences with horn is that if you look at it, the fibers in it grow straight and lengthwise. I wonder if that plays a part in horns unique sound? I think the fibers in the horn "carry" the sound as the air flows in the same direction as the fibers and allows the reed to want to vibrate in the same direction making for a concentrated direction of energy? If that makes any sense? I guess what I mean is that it just all flows the same way when you blow on the reed. With other materials, like acrylic and delrin, you dont have that flow as the material is solid and uniform in it's density. The natural fibers in the horn, along with the fact that they grow in a straight line, allow or even force the air to move just a bit quicker and vibrate the reed just a tad bit faster giving it that nice clear crisp sound.
Anyway, it's just a thought - I really have no idea but I do know there is a difference in sound from one material to another. Figuring out why is probably not as important as knowing how to put those differences to use when making a call for a specific sound.
Still, one heck of a nice looking call.
Al @ THO