The theoretical study of traditional Korean music was centered on the theory of scale and Jangdan(rhythm pattern), but the structure of the melody of traditional Korean music was systematically established by Dr. Lee Hye-gu. Lee Hye-gu classified the composition of the melody into Sigimsae(ornamental note as a change in the main note), Jangsigum (ornamental notes), Ganjeom(melodic notes), and Wonjeom(structural notes). He maintained that a melody consists of Sigimsae and ornamental notes, melodic cell, and melody, and the Sigimsae and ornamental notes are expanded to form a melodic cell, and the melodic cells are gathered to form a melody. The melody is divided into beginning, middle, and end. The beginning is divided into high start, middle start, and low start, and the middle part is classified into upward, horizontal, downward, convex, and concave melodies, and the end is described as various types of half cadence and perfect cadence. Lee Hye-gu classified Sigimsae as a change in the main note, and ornamental notes added to the main note, but did not distinguish them by a layer of melody, and viewed Sigimsae and ornamental notes as one layer. In his melody theory, Lee also did not explain the structure of the melody itself since he saw it as a combination of melodic patterns. In Lee Hye-gu’s study, ‘expansion’ means the expansion of the number of notes, the width of the pitch, and the length of the note. If Sigimsae is a change of the main note and ornamental notes are added sound, ornament melodic patterns can be an extension of Sigimsae melodic patterns. On the other hand, if a melody is composed of the layer of Sigimsae, ornament melodic notes, melodic notes, structural melodic notes, its each melody can be identified as the Sigimsae melodic pattern, the ornament melodic pattern, the melodic pattern, and the structural melodic pattern. In addition, a method of extracting common notes was used to distinguish the melodic pattern on each layer, and a method of analyzing the melody was presented by finding the original melody except for Sigimsae, ornament melodic notes, and melodic notes, respectively. As a change in the main note, there are four types of Sigimsae, Yoseong(vibrato), Chuseong(upward portamento), Toeseong(downward portamento), and Jeonseong (sforzando), described in Samjukgeumbo. They have functions to decorate the progress of notes and melodies and also give the characteristics of the mode. Sigimsae can be explained by up(Chuseong), down(Toeseong), fast up+down(Jeonseong), and repetitive up+down(Yoseong) depending on the direction of change. Ornament melodic pattern can be divided into up(Chuseong), down(Toeseong), fast up+down(Jeonseong), and repetitive up+down(Yoseong) types if they are enlarged types of Sigimsae, and can be divided into upward, parallel, downward, convex, and concave types. Since the melodic pattern is also a movement of melody, it can be classified into up, parallel, down, convex, and pentagonal types. In addition, the melodic pattern decorates the structural melodic pattern, and even the same structural melodic pattern shows different expressions depending on the melodic pattern. The structural melodic pattern can be shared between each melody and even between songs, and throughout Korean traditional music, the structural melodic pattern with a four-degree descending structure is widely used. In front of it, there is a structure of change in the low start, the medium height start, and the high start.