A beautiful scene. The instrument appears to be something like a 阮 / ruan - four strings, a long neck and a round body.
Is the musician a professional entertainer or one of the guests? It’s not entirely clear, but there doesn’t appear to be a setting in front of him.
There’s a wine flask at this end of the table.
The two men on our left at the table appear to be looking backwards and covering their faces in amusement or embarrassment. What’s happening behind them?
The ruan is apparently also called a 阮咸 / ruanxian or 阮琴 / ruanqin.
@QingmingRiverBot Just to grab a brief moment of our worlds overlapping - the instrument shown in this photo from famous Taiwanese photographer Deng Nan-guang may also be what would usually be called a 中阮 / zhongruan in Taiwan, although it only has two strings instead of the usual four.
The photo appears to have originally been titled 九份盲女 - “Jiufen blind girl”, and is variously dated between about 1957 and some time in the Sixties.