Modernized, newly composed gayageum music was activated in the early 1960s and has been developed by many composers. In this process, works that have been steadily performed for decades have been recognized as representative of newly composed gayageum pieces and are often used not only for performance but also for education and evaluation. The purpose of this study is to seek and present the notation method and effective performance techniques representative works. It examined the creative world of composition by Paik Byung-Dong, Yi Sung-Chun, and Lee Hae-Sik, representative composers of newly composed pieces. From the three renowned pieces, “Jeongcwhi”, “Noriteo”, and “Heukdam”, the notation and performance techniques of each composer’s distinguishable performance style were reviewed. The findings are as follows. First, the Arabic numeral on the note means the finger number in “Noriteo” while it means the string number in “Heukdam”. There is no case where numbers are written on the note in “Jeongcwhi”. Second, the harmonics technique is marked as ○ in “Jeongcwhi”, ◆ () in “Noriteo”, and 8va in “Heukdam”. Third, in the case of pressing a string to make a sound, it is not indicated in “Jeongcwhi” while it is in “Noriteo”. In “Heukdam”, the performer determines whether to press according to the string number written. Fourth, in terms of nonghyeon's notation, it is not indicated in “Jeongcwhi, but in “Noriteo”, it is marked as , and when two strings are pressed at once, it is written as . In “Heukdam”, the regular nonghyeon is indicated by , the thick nonghyeon is indicated by , and jeonsung is indicated by , and special attention should be paid to the indication of nonghyeon for two-note or more harmonies. (note that represents jeonsung only for the lower note for two-note harmonies.) Performance techniques for effective expression were presented by considering each composer’s creative worlds of and the notation method of representative works and can be summarized as follows. Paik Byung-Dong's works should be played with an understanding of the instrumental system of Western string instruments and paying attention to the composition of the main notes presented in the tuning method and the progress of the microtonal notes. The left-handed technique can be freely expressed in nonghyeon by the competence of the performer. Yi Sung-Chun's works are meticulously written on expressions as well as notes on finger numbers, right and left hand performances, so it is important for the performer to refrain from arbitrary expressions and play exactly as the composer intended. It should be noted that Lee Hae-Sik's works include notes such as string numbers, left-handed notes, notes with and without nonghyeon in harmony that are not commonly used, and should understand the system of rhythm and play harmonically with janggu.