This paper is analyses of the musical structure and the dicourse of Sanjo by comparing Sim Jungsun, Kim Haesun and Sim Sanggeun's Gayageum Sanjo recorded in the mid-1920s about their Jangdan-column, melodic development, phrasing, tonality, movement of keys, and etc. In the cases of Sim Jungsun, Kim Haesun's Sanjo, each deserves to represent the locality of their native place as their musical style, training and background are different and there are on example before them. The former Kyeongki․Chungchung province the latter Kyeongsang․Jeonla province. However, Sim Sanggeun who succeeded to Sim Jungsun's music as a nephew is not a regional representative of Kyeongki․Chungchung province. Because his music share the characteristics of the Sanjo with both Sim Jungsun and Kim Haesun's ones. So I criticized the genealogy of Sanjo based on locality.It was needed the dicourse of genealogy to designate the Important Intangible Cultural Heritage after Korean Liberation. It was useful to persuade the society to preserve Sanjo as the Korean musical heritage in a crisis of extermination, it was in the way of certifying its artistic nature. There are some samples outside of a certain genealogy, it make them others. It makes difficult to explain the variableness of the style of Sanjo, because genealogy misguides Sanjo history as directly developed. In this point the dicourse of genealogy in Sanjo deserves to be non-artistic idea. The dicourse of genealogy based on oral statement of the insider informant is actually against the practical progression of Sanjo even in some places. So genealogy which embodies the locality is unnecessary to criticize creativity of the Sanjo in Korean Music history after the mid-1920s.