Oh Yong-rok(1955~2011) was a Korean music scholar and composer. Despite of his short life, he made a considerable achievement in Korean music world as a serious scholar, excellent composer, and potent critique. In memory of the tenth year of his death, I will examine his academic activities in this keynote speech. Oh Yong-rok was interested in the systematic study and historical study of Korean traditional music. The former is resulted in his ‘discourse of tone cluster,’ and the later in his ‘discourse of formation.’ Oh was thoughtful to discover the essential relatedness of tones in music. He tried to find the nuclear tone and the supplementary tones that was resulted in the ‘dynamic modal theory.’ In this way his approach is ‘melodic theory’ rather than ‘modal theory.’ Oh endeavored to explore the historical formation of traditional musical pieces. Based on the new interpretation of old musical notations he gave a new light on the historical development of the court music. Oh made a significant step in the advance of Korean musicology. It is the mission of the next generation to further his academic accomplishments.