This paper investigates into a lost koˇmun'go tablature attributed to Soˇnghyoˇn callcd hyoˇnguˇmhapjabo[現金合字譜]. based on evidence drawn from hyoˇnguˇmhapjaboso written by the same author. Up to the present, the historical value of hyoˇnguˇmhapjabo[現金合字譜] has been largely overlooked by most Korean scholars. However, an introduction to this document provides important insights into the state of koˇmun'go music during the 15-16th century. Besides, the koˇmun'go tablatures from 16-17 centuries indicate that even prior to Kumhapjabo. the earlist extant koˇmun'go tablature. there was another notational system for the instrument and that Soˇnghyoˇn was possibly the editor. This allows present-day scholars to make some conjectures regarding the possible nature of the lost noation. This study, after examining the various writings of soˇnghyoˇn and other 16-17th-century sources, reconstructs the background and the contents of hyoˇnguˇmhapjabo. With the aid of his brother, a connoisseur of music. Soˇnghyoˇn. was able to learn the arts of koˇmun'go from the contemporary master Yi Ma-ji(이마지). After this initial contact, soˇnghyoˇndvoted his to music. occasionally learning from and exchanging artistic ideas with masters like Yi Ma-ji. Kim Pok-kuˇn (金福根). and Choˇng Ok-kyoˇng(鄭玉京). From as early as 25 years of age. Soˇnghyoˇn was reknowned as an authority in music, which led him to hold an important position at the Changakwon. after being appointed a goverment official. It was during this period that soˇnghyoˇn was exposed to Chong In-ji's influence and his important book Yulnyo-sinso(律呂新書). which further expanded his knowledge in music. Such a long period of accumulating knowledge in koˇmun'go music foregrounded soˇnghyoˇn's invention of a koˇmun'go notational system and his publication of hy on gu mhapjabo. Therefore one can safely conclude that his work epitomizes his in-depth understanding of the koˇmun'go tradition and that he intarded it as a solution to his life-time concern that the traditions of koˇmun'go master were dring without being faithfully transmitted. The tablature was intended to serve the needs of students who learned koˇmun'go without neccedssarily having a teacher to guide every step. The actual content of hyoˇnguˇmhapjabo is surmised to have been comprisad of yoˇmilnak, pohoˇja, kamgun'un, halnimbolgok. Taeyoˇp. and pukjoˇn The introduction to kuˇmhapjabo states that there was already a tablature before the mid 16th century. with a rather inconsistent notationa system and that kumhapjabo is merely a re working of that prototype with the addition of a few new pieces. This points to the possibility that the system at issue is actually S oˇ nghyoˇ's hyoˇng uˇmhapjabo, of which kuˇmhapjabo is simply a revision. There soˇnghyoˇn's hyoˇnguˇmhabjabo, although lost, bears the historcal significance of having been the very first koˇmun'go tablature ever written in the hapjabo notational system. Further, the existence of an earlier tablature than Kuˇmhapjabo(琴合字譜) may help explain the structure of the pieces contained in kuˇ mhapjabo that are presumed to have had a longer history. (November 9, 1997)