I am going to examine the late Dr. Jang, Sa-hun's theoretical study on Korean music from the point of the pitch, the length, the colour and the texture. In the Choesin gukak chonglon ("The Introduction of Korean Music", 최신국악총론, published by Segwang Music Press, 세광음악출판사, 1985), one of his representative works, Dr. Jang had already shown his ideas on the four points of Korean music, which I just mentioned the earlier. The pitch system of Korean music has five steps such as elementary tone (tuning tone), tone system, scale or the mode, the tori (토리) and the melody. Dr. Jang insisted that the minor third interval existed between the elementary tone of A-ak (아악) and Hyang-ak (향악) had not been found at the times of King Sejong when Akhakgueheom (악학궤범) was published, around 15th century, in Choseon dynasty. Dr. Jang described well the scale and mode of the Jeongak (정악, Court music) and Minsokak (민속악, Folk music). His scale theory tends to be appeared as modulation (변조). Tori (토리) includes the scale, the function of the tone, the type of the ornamentation and a method of the melodic progress. Dr. Jang described an interval, Yoseong (요성), Toeseong (퇴성), ornamentation, finale, and melodic type, while he was explaining the mode of the Minsok-ak (folk music, 민속악). This method is regarded as the major concept of the tori(토리). However, his explanation is not enough to identify scale, mode, tori(토리) and seem to fail to explain the concept correctly. I think that's his limitation. As for the research related to the melody, Dr. Jang explained the melody of finale. Also, he mentioned the method of inserts an ornamental tone in the major tones of melody. However, in my view, he lacked full explanation of the melody. The length of tone consisted with five steps such as beat, meter, Jangdan (장 단), rhythm and melody. Dr. Jang's study about the length of tone told us only about Jangdan (장단). Among this, the section of Maehwajeom Jangdan (매화 점장단) is worthy to discuss. However, this, too, is a simple explanation. I think more research should have been done than this. There is no particular thing to be discussed in Dr. Jang's study of the tone colour, except the research of the change of the vowel by the song. (변모음) However, I think even the change of the vowel is not enough to be paid attention because it is Dr. Jang's personal opinion. Dr. Jang's research on the result of texture in Korea music is somewhat inconsistent with each other so there is no form to be explained under the same level. In summary, the characteristic of Dr. Jang's theoretical research on Korean music was the fact that it was an analyzation used by a real music and that he had drawn some musical rules out of it. I think that it was possible because he was a Geomungo(거문고) player. One hand, however, the theatrical thesis is not clear enough while his musical analyzation seemed to be successful. But, more importantly, his studies has still had a great influence on Korean music theory.
한국국악학회는 국악을 연구하여 음악학 및 민족음악의 향상에 기여할 목적으로 1948년 4월 봄에 이혜구, 장사훈, 성경린, 이주환 외 15명의 발기로 발족하여 1963년 12월 14일 사단법인체로 인가취득한 이래 1) 국악의 연구발표 2) 국악 관계자료서 수집 3) 국악에 관한 전시회 및 강연회 개최 4) 국악에 관한 출판사업 5) 국내의 학계간 교류 등의 사업을 진행해 오고 있다. 본 학회는 국악의 연구발표를 4000여회에 가까운 월례발표회를 가졌으며, 20회에 걸친 국악기 및 국악서적 전시회를 열고 3회의 신국악작곡 발표회를 가진 바 있다. 특히 학회에서는 1971년 한국음악연구 제1집을 발간한 이래 현재 제45집 출판에 이르렀으며, 30여종의 고악보 간행, 이혜구 박사 송수기념 음악학 논총, 장사훈 회갑기념 동양음악논총 등 30여권의 단행본을 출판하였다. 또한 1989년 제1회 국악학 전국대회를 열어 한국음악의 쟁점이 되는 주제를 선정하여 전국규모의 학술대회를 개최하고 있으며, 1975년 한·일간의 고려악 연구회를 발족시켜 일본의 음악학자들과의 공동연구로 심포지움을 개최하였으며, 1981년에는 국제전통음악학회(ICTM) 서울대회를 치뤄내고, 1994년에는 제1회 아시아 태평양 민족음악학회(APSE)를 서울에서, 1999년에는 제6회 아시아 태평양 민족음악학회(APSE)를 수원에서 성황리에 치뤄내는 등 외국학회와 교류에 힘써왔다.