Double-neck Guitar!
I made two improvised pieces on a guitar hand-built by Ozma Instruments’ Jeffrey Schreckengost. Jeff made this guitar for me back in 2012 or so, and while I’ve used it on records, in live situations, and to score dance pieces, I never made any videos of it.
18 strings over two necks, including two fretless bass strings and five different string doubles. A beautiful instrument. Have a listen/watch.