This study conducts a systematic examination of the 11th-century Minamoto no Tsunenobu Biwa Fu (源经信琵琶谱),held in the Archives and Mausolea Department of the Imperial Household Agency,Japan.Through codicological analysis,symbolic deconstruction,and comparative research with Tang-dynasty biwa tablatures and the Japanese Nangū Biwa Fu (南宫琵琶谱,920 CE),we reveal its role in the early Japanization of biwa notation,evidenced by innovations in pitch characters and performance symbols.Crucially,by identifying restoration errors in later conservation and conducting textual criticism,we concretely demonstrate its inheritance and development of the chōshikyoku (调子曲,modal preludes) from the Nangū Biwa Fu.These findings establish this manuscript as a chronological benchmark within the East Asian biwa lineage—positioned between the Nangū and Sangoyōroku (三五要录) traditions—while deepening scholarly understanding of Japan's transformative adaptation of Tang-Song musical systems during their eastward transmission.