Wang San-ak
Wang San-ak was the prime minister of Goguryeo during the reign of King Yangwon.
According to the Samguk Sagi, written in 1145, the geomungo was invented by him by using the form of the ancient Chinese instrument guqin. After his death, the instrument was passed down to Ok Bogo, Son Myeong-deuk, Gwi Geum, An Jang, Cheong Jang, and Geuk Jong, while being widely spread over the kingdom.