An adapter for sticking a saxophone or clarinet mouthpiece onto 1/2" PVC pipe for making your own instrument-like-thing.
Someone gave me an old mouthpiece - I think it's from an alto sax, but I don't know for sure. I made this simple OpenSCAD script for an adapter to plug the mouthpiece onto the end of a length of 1/2" (ID) PVC pipe. It does the job.
This particular mouthpiece has a conical end, about 24 mm long, which tapers from 26.6 to 24 mm. It should be easy to adjust the OpenSCAD file for slightly different shapes and sizes.