This goofy little instrument is kind of like a bugle, but instead of modulating the tone by pursing your lips, the tone is changed by varying the tension in a membrane that creates the vibration. It consists of a horn with a membrane stretched across the narrow end. There is also a concentric tube around the outside of the narrow end where you blow air in. The air pressure forces the membrane outward, where it escapes over the inner rim and thru the horn, causing the membrane to vibrate in the process. Many thanks to Fabien T. who's PVC Membrane Clarinet inspired this design. (He's also got a link to a great video by Nicolas Bras, who came up with the membrane reed concept.)

For the membrane, you'll need a small sheet of rubbery material like cut open balloon, or a latex or nitrile surgical glove. (A glove is easier to work with because it will lay flat.) The membrane gets glued to a threaded ring, which is then used to pull the membrane down uniformly over the end of the horn. Screwing the membrane tighter increases the tension and raises the pitch. Loosening the ring lowers the pitch.

With the original clarinet version, the length of a straight-walled tube (or the open hole positions) determines the tone. This instead uses a flared tube that will resonate at whatever frequency the membrane wants to vibrate at.  This allows the tone to be varied with the membrane tension.

Printing
I printed mine in PLA with 0.2mm layers. Most any settings will work as long as the resolution is fine enough to reproduce the fairly fine screw threads.

Assembly
First look at the inside of the ring and notice that the treads run all the way up to one side, but the other side has a smooth section. The end that's smooth inside is the side that will be glued to the membrane. 

Start by laying out the membrane material on a flat surface. If it is wrinkled, stretch it flat with some pieces of tape around the perimeter. Next, apply a thin, uniform bead of superglue (cyanoacrylate) to the end edge of the ring. (Remember, the smooth-inside end.) Carefully place the glued end down on the membrane and hold until the glue is set.  Superglue sticks very well to both nitrile and latex.

When the glue is dry, trim the edges flush with scissors. Now screw the other end of the ring onto the bugle until the membrane is just touching the narrow end of the horn. As you blow into the mouthpiece, tighten the ring slowly until you get a tone.  From here, just adjust the ring to get the hang of playing different notes.