I have already discussed several microtonal guitars in this series. This next guitar is one of the most unusual. Dave Keenan is the inventor of the Choob, a tubular (choobular?) electric guitar.
This picture is of the first microtonal choob. It has eight strings and is tuned to a seven limit schismatic temperament. One of the chief advantages of this design appears to be the ease with which you can setup a microtonal fret layout or even change it if you aren't satisfied. The frets are monofilament that are threaded through drilled holes. You can drill new holes if you want to change the fret layout.
The use of a light weight tube requires some wet sand for ballast and an internal truss wire system to counteract the tension of the strings. There are also plans to include a neon tube to light up the frets at night.
It looks like the curved fretboard would make it difficult to play, but the reports I've heard indicate that it's much easier than it looks. The curved design also makes it possible to use a bow. I don't really need a microtonal guitar at the moment, but if I ever decide to get one, I will definitely consider this new design.
Another recently invented microtonal instrument is the udderbot. The invention of the instrument was a collaborative effort that took place in the vicinity of Jacob Barton. I don't know much about it since it's new and the web site is still under construction. I could describe it, but I thought it might be more fun for you to try to guess its general appearance based on the name, udderbot. You can then check the website for pictures and further information.