The Yueshu yaolu 樂書要錄 "Important Records about the Writings on Music"
is a compendium on music compiled on imperial order of Empress Wu Zetian 武則天 and under the supervision of Yuan Wanqing 元萬頃. Yuan Wanqing (ca. 640-690) was a descendant of Emperor Jingmu 景穆皇 (Tuoba Huang 拓跋晃, dynastic title Emperor Gongzong 魏恭宗, the oldest son of Emperor Taiwu 魏太武帝) of the Northern Wei dynasty 北魏 (386-534). During the Qianfeng reign 乾封 (666-667) of the Tang period 唐 (618-907) he participated in Li Ji's 李勣 Korea campaign, but was exiled because of an unappropriate use of language in a memorial to the throne. After several years he was called back to the court, where he became a court official and became an important editor of a series of publications promulgated by Empress Wu (r. 690-704) and compiled the books Lienüzhuan 列女傳 (a new edition), Chengui 臣軌, Bailiao xinjie 百寮新戒 and the Yueshu yaolu. During the Yongchang reign 永昌 (689) he was again exiled and died in southern China.
The 10 juan "scrolls" long book was finished in 700 CE but was soon lost. A copy was brought to Japan by Kibi no Makibi 吉備真備 in 735, but of this specimen, only juan 5 to 7 have survived. These fragments returned to China in the late 19th century and were published in the collectanea Yicun congshu (Isson sōsho) 佚存叢書, Wanwei biecang 宛委别藏, Zhengxuetang congshu 正覺樓叢書 and Congshu jicheng chubian 叢書集成初編. The surviving part of the Yueshu yaolu gives an impression of the high standard of music during the Tang period 唐 (618-907) that differed from that of earlier ages, but also from the practice of music during the Song period 宋 (960-1279).
The 5th scroll consists of 10 chapters of a theoretical nature. The first chapter (Bian yin sheng shen sheng yuan 辨音聲審聲源) includes a quotation from Cai Yong's 蔡邕 text Yueling zhangju 月令章句, where it is said that in ancient times people used to tune the pitchpipes by hearing (yi er qi qi sheng 以耳齊其聲), in addition to mathematical calculations concerning the length and volume of the pipes. In the chapter Lun er bian yi 論二變義 the alteration of the two tones gong 宮 and zheng 徵 are explained. Other chapters of juan 5 are also dedicated to this theme, like Qi sheng xiang sheng fa 七聲相生法 (describing the relation of each tone from a preceeding one, in a system similar to the phenomena of the calendar, li ba xiangsheng yi 曆八相生義), Lun xiang sheng lei lie 論相生類例 (discussing the position of the basic tone of a gamut) or Qi sheng ci di yi 七聲次第義. The chapter Lun sanfen sunyi tong zhu xuan guan 論三分損益通諸弦管 discusses the method of producing a new tone in the gamut by adding or deducting a third to or from the length of the pipe or string (sanfen sunyi fa 三分損益法). In the final chapter Yuepu 樂譜 the use of pentatonic music in daily life is dealt with.
The 6th scroll describes the system of the musical modes and pitchpipes and quotes extensively from older writings, like treatise on astronomy and music Lüli zhi 律曆志 in the official dynastic history Hanshu 漢書, the Yueling zhangju 月令章句 or Sanli yizong 三禮義宗. In includes four chapters describing the dimensions of the pitchpipes and the lengths of strings and their relations to the universe (Ji lülü 記律呂), "harmonious chant" (Qiankun chang heyi 乾坤唱和義), observing the "right weight" (Jin quanliang 謹權量, where the dimensions of the pitchpipes are related to other measures) and the correlation of the pipes with the season (Shen feihou 審飛候).
The 7th scroll includes three chapters on modulation (Lülü xuangong fa 律呂旋宮法), harmony (Shisheng lüfa 識聲律法) and the seven musical keys (Lun yi lü you qi sheng yi 論一律有七聲義). The sequence of modulating the keys is described, in "clockwise direction" (shunxuan 順旋) and counter-clockwise (nixuan 逆旋). This is the first instance in Chinese literature on music that modulation is concretely described.
The Yueshu yaolu included five charts illustrating the harmonious "birth" of the next tone in a gamut (Qiankun changhe tu), the method of enclosing the circle of the twelve pipes in a sealed room to analyze their relation to the months (Han lü shi tu shi'er lü xiang sheng tu 漢律室圖十二律相生圖), and illustrations to the seven different tonal positions of an individual pipe (Yi lü you qi sheng tu 一律有七聲圖).
Quotations from the other parts of the Yueshu yaolu are to be found in Japanese texts on music, but until now there has not been made a systematic collection of these fragments. The book Sango yōroku 三五要錄, for instance, quotes from the modulation of the pipa lute (pipa xuangong fa 琵琶旋宮法), and the book Agetsu mondō 阿月問答 from juan 10, and the text Onritsu tsūchishō 音律通致章 gives an overview of the central chapters of the Yueshu yaolu. Fragments can also be found in the books Shōmei yōshin shū 聲明用心集, Ruihitsu jiyō 類筆治要 and Taigenshō 體源抄. Important Japanese studies on the Yueshu yaolu have been written by Hazuka Keimei羽塚啓明 (Gakusho yōroku kaisetsu 楽書要録解説 and Kōi Gakusho yōroku 校異楽書要録).
Huang Xiangpeng 黃翔鵬 (1989). "Yueshu yaolu 樂書要錄", in: Zhongguo da baike quanshu 中國大百科全書, Yinyue wudao 音樂 舞蹈, Beijing/Shanghai: Zhonguo da baike quanshu chubanshe, p. 837.
Li Xueqin 李學勤, Lü Wenyu 呂文鬰 (1996). Siku da cidian 四庫大辭典, Changchun: Jilin daxue chubanshe, vol. 1, p. 623.
Luo Chuankai 羅傳開 (1992). "Yueshu yaolu 樂書要錄", in: Wu Jie 吳杰 (ed.), Riben shi cidian 日本史辭典, Shanghai: Fudan daxue chubanshe, p. 297.
Wang Yusheng 王譽聲 (1996). "Yueshu yaolu 樂書要錄", in: Zhongguo xueshu mingzhu tiyao 中國學術名著提要, Yishu 藝術卷, Shanghai: Fudan daxue chubanshe, p. 35.
Wu Feng 吳楓 (ed. 1987). Jianming Zhongguo guji cidian 簡明中國古籍辭典, Changchun: Jilin wenshi chubanshe, p. 264.