It is made from the protective case for a 12 cc hypodermic syringe, which can be purchased from a pet store or veterinary supply store. I use the syringes as tools for extruding silicone rubber in making silicone rubber sculptures. This is a good way to recycle the protective cases.
The needle cover (pink) is sanded down to make the mouthpiece. The reed is cut from a piece of scrap plastic that I recovered from a junked flat screen monitor. Electrical tape holds it all together.
To protect it in my pocket, I made a carrying case out of PVC pipe.
To hear how the hypotooter sounds, listen to the .mp3 audio file in the last step.
Step 1: The Syringe
Step 2: Forming the Mouthpiece
To sand the curve, use a forward and backward motion, with a little extra wrist action. Make sure the curve has no flat spots and that both sides are sanded with the same curve. Once you get the arm and wrist motion down, it becomes almost automatic.
Use course sandpaper first, then medium, and then fine. Remove edge burrs with a very sharp X-acto craft knife, or something similarly precise.