Gujin yuelu 古今樂錄 "On old and modern music" was a book on musical theory written during the late Southern Dynasties period 南朝 (420-589) by the Buddhist monk Zhijiang 智匠 (fl. 567; perhaps identical with Zhiqiu 智丘, also written 智邱). It is lost since the Song period 宋 (960-1279), but fragments were collected during the Qing period 清 (1644-1911) by Ma Guohan 馬國翰 (1794-1857) and are found in his series Yuhan Shanfang ji yishu 玉函山房輯佚書. The original length was, according to different book catalogues, 12 or 13 juan.
The book was based on the belief that time and "spirit" in the air (houqi 候氣) had an influence on musical temperament. It also contained stories of songs composed by the mythological Emperor Yao 堯, Xu You 許由, King Wen 周文王 of the Zhou dynasty 周 (11th cent.-221 BCE) and the philosopher Zhuang Zhou 莊周 (trad. 369-286 BCE), songs created by Wang Daochong 王道沖 and Lu Ji 陸機 (261-303) during the Jin 晉 (265-420) and Liu-Song 劉宋 (420-479) periods and discussed the reasons for their names. There was also a section on foreign musical instruments.
The preserved fragments are also included in Wang Mo's 王謨 (c. 1731-1817) series Han-Wei yishu chao 漢魏遺書鈔 and Ji Liankang's 吉聯抗 (1916-1989) Gu yueshu yiwen jizhu 古樂書佚文輯注.