3 string fretless board zither

This electric instrument is technically a 3-string fretless board zither, played flat lap style with the highest string closest to the player (like a Guqin or a mountain dulcimer). It is strung with the 3 lowest strings of an electric guitar: a .048 tuned up to G, a .044 tuned to A, and a .034 tuned to D.  GAD is a folded fifth tuning, which gives you open intervals of a major second (G-A), a fourth (A-D), and a fifth (G-D)

http://www.guitarmoderne.com/artists/spotlight-instant-takemitsu