I created this model completely in fusion 360, so it is entirely smooth. This was mostly made as a proof of concept, but it turned out well. I planned on adding texture and details in another program, but that might be a while(feel free to remix it).
I have included the full version,(~660mm tall) and a version broken into 3 pieces. The 3 pieces are designed to fit all together on an Ender3 size bed, and I was able to print them without supports(I did use rafts for better bed adhesion). The full size model can be resized and cut up however you'd like. I tried forming a lip on the mating surfaces, but was having difficulty with the twisting shape, therefore the joints are all flat.
Blowing the horn takes some practice. If you have ever played a brass instrument, it is similar. I modeled a mouthpiece into the horn and it does work, but if you have bigger lips like I do, you might find it easier to form a mouthpiece with your thumb and forefinger.
The author marked this model as their own original creation.