Wang Shan Mountain

Japanese: 王山岳 - おうさんがく

...Today it is called the Xuanqin. It is said that Wang San-ak made the geomungo to imitate the Chinese zither, and in the murals of the Dance Tomb in Maruto, a four-stringed, 17-fret geomungo is depicted along with the ruan xian, horn, xiao, waist drum, and flute. Goguryeo music was adopted as Goryeo-gui, the third of the seven musical instruments of the Sui Dynasty in China, and it is said to have been a bugaku dance using 14 types of instruments.

From [Pakku]

…In 1427, he perfected the twelve-tone scale with his own Huangzhong and Henkei (playing instruments), and organized the musical system. In 1431, he abolished the hyanggaku (a traditional music played at the palace's morning assemblies) and adopted Chinese gagaku (traditional court music), the scores of which are recorded in the Annals of King Sejong. He is called one of the three great musical masters of Korea along with Wang Sanak of Goguryeo and Uruk of Silla, and is highly acclaimed alongside the contemporary scientist Chiang Young-sil. [Mitsuo Yoshida]…

*Some of the terminology that refers to "Oshan Mountain" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…今日では玄琴と呼ぶ)がある。コムンゴは，王山岳が中国の琴を模して作ったといわれるが，丸都の舞踊塚壁画には，阮咸（げんかん），角，簫（しよう），腰鼓（ようこ），横笛とともに，4弦17棵(フレット)のコムンゴが描かれている。高句麗の音楽は，中国隋の七部伎の第3番目に高麗伎としてとり入れられたが，それは14種の楽器を使用した舞楽であったという。…