The ruan (阮) or moon guitar is a four-stringed Chinese instrument similar to the pipa. It is also sometimes called the qin pipa (秦琵琶) and ruanxian (阮咸).
The most common ruan is the zhongruan (中阮) or tenor ruan. The bass ruan (大阮) is also fairly common; less frequently heard are the soprano (高音阮), alto (小阮) and contrabass: Diyinruan (低音阮) versions.
This video was shot and edited by Jonah Kessel.