https://en.m.wikipedia.org/wiki/Zhongruan
https://en.m.wikipedia.org/wiki/Ruan_(instrument)
The round instrument is a zhongruan mostly tuned G2 D3 G3 D4 and played with fingerpicks.
Some players tighten the strings a bit to GDAE same fingering as octave mandolin, mandolin, violin. This lets...