In form, this instrument is a simple box zither. What’s unusual is the sounding method. Rising vertically from each of the main strings is a second, much lighter string, attached to a yoke above. The main strings are sounded by stroking the lighter vertical strings with rosined fingers. This sets up a stick-slip vibration which is transmitted to the main string. It’s quite an efficient system: the up-and-down stroking of the vertical string gets the main string going the right direction to drive the soundboard very effectively. The resulting tone is coarse, with an unusual tone quality, and it’s satisfyingly loud.
In addition to the video linked below, this instrument is also featured here.