Gachang-Gasa (歌唱歌辭) refers to works within the literary category of Gasa (歌辭) that are recognized for their singability. These works expanded into the scope of Gasa (歌詞) through musical development in the late Joseon period. However, there are various perspectives on whether the lyrics of Gasa (歌詞) fit within the format of Gasa (歌辭). This study aims to identify the literary and musical connections between early Joseon's Gachang-Gasa (歌唱歌辭) and the later Gasa (歌詞). Early Joseon Gachang-Gasa was generally composed of melodies from the Goryeo period but displayed various forms, making it difficult to define a single musical characteristic. This is because Gachang-Gasa was a literature-based category, sung without a fixed melody and adapted to the situation. In the late Joseon period, Gachang-Gasa works began to appear in music collections and scores, distinguishing themselves from Gagok and including works that are part of the 12 Gasa (歌詞). Some Gasa works strictly adhered to the four-beat Gasa form, but most disrupted this rhythm. Musically, however, they were composed in a strophic form with repeated melodic progressions. Since Gachang-Gasa and Gasa are categories based on literature and music respectively, understanding them as continuous can lead to contradictions. Therefore, Gachang-Gasa and Gasa should be understood by categorizing works that are sung without a specific musical form as literature, those that qualify as Gasa both literarily and musically, and those based on a specific musical form as Gasa. Among these, , , and belong to both categories, playing an important role in transitioning from early Joseon Gachang-Gasa to later Gasa. Subsequently, Gasa developed with an emphasis on the musical characteristics of these works, establishing itself as an independent musical category separate from the literary category. Therefore, , , and are seen as foundational works of Gasa and deserve attention for their role in bridging Gachang-Gasa and Gasa.