Bak Yeon

Bak Yeon or Park Yeon (; 20 August 1378 – 23 March 1458) was a government official, scholar, writer, astronomer and musician in the Early Joseon Dynasty period, who was a teacher of King Sejong and created Armillary sphere Honcheonui, Water clock Borugak Jagyeongnu and sundial Yangbu Ilgu along with Jang Yeong-sil and five basic sounds(Gung, Sang, Gak, Chi, Wu), which corresponds to five consonant groups (Aeum, Seoreum, Suneum, Chieum, Hueum) in Hunminjeongeum. He has also adapted court music to the new Confucian philosophy, particularly in the concept of ''yeak'', a Confucian ideology that combines ritual and music.

He made appeals to the king Sejong 450 times for the necessity of organizing the imperfect musical instrument coordination and compiling the sheet music, and correctly measured the notes according to his own 12 notes. And this has reformed the court music in general. Along with Wangsan of Goguryeo and Ureuk of Silla, Bak Yeon is considered one of the three most popular music saints in Korea. Provided by Wikipedia