Customary book
The customs book was the office that was in charge of practical exercises of music in the early Joseon Dynasty. It seems to have been established at the end of the Goryeo period, as it is mentioned in the "Koryo-ja" It is an institution that has been practicing the practice of the accompaniment of the evil and the blind and the song here. He chiefly practiced practical exercises for playing musical instruments and percussion, which were mainly used in court feasts. In addition, when Sejong created a new song and created a new song, he also took on the task of adjusting to the melody of high tide. In addition to the theory of music, which was mainly responsible for music theory research, he was dualist in music administration in early Joseon Dynasty.