I designed and made a new instrument a couple of weeks ago. I call it the shakuflexophone.
It's made from 20mm PVC pipe. I jammed a pipe connector onto the end, which I cut and filed into the shape of a shakuhachi mouthpiece.
The instrument including the mouthpiece is in total around 42cm long. I cut a slit into the pipe, approximately 3mm wide, from the tail end to about 3cm before the mouthpiece.
I cut a ring from 25mm PVC pipe, and cut through the ring so I could open it out enough to squeeze it onto the opposite end of the instrument to the mouthpiece. I then drilled a small hole in the ring and screwed a 5cm screw into it so about 3.5cm is protruding on the outside and around 1cm on the inside, through the slit.
Next I got the fattest rubber band I could find (about 15mm wide) and cut it so it became a rubber strip. I taped one end to the pipe between the mouthpiece and the slit, and fastened the other into a bulldog clip. The "arms" of the bulldog clip fit nicely over the protruding screw.
Oh, and I had some yellow spray paint for some reason, so I sprayed it yellow.
The instrument is played like a shakuhachi, but without fingerholes. Instead, the player's fingers are used to hold the strip of rubber down over the long slit. This gives the player a sliding scale to play with, like a violin or fretless bass. It's similar to the shakuhachi in that it's probably very difficult for beginners to get a sound out of, and I would say that it's even harder to play in tune than a conventional shakuhachi.
I haven't seen an instrument quite like the shakuflexophone before, but it was inspired by some ideas in Bart Hopkin's excellent book Musical Instrument Design.