Gu yueshu 古樂書 "Old books on music" is a critical collection on texts on music compiled during the early Qing period 清 (1644-1911) by Ying Huiqian 應撝謙 (1615-1683), courtesy name Siyin 嗣寅, style Qianzhai 潛齋, who hailed from Hangzhou 杭州, Zhejiang.
The first part of the 2-juan long book, finished in 1678, is a rearrangement of Cai Yuanding's 蔡元定 (1135-1198) book Lülü xinshu 律呂新書 from the Song period 宋 (960-1279), with quotations from the Neo-Confucian scholar Zhu Xi 朱熹 (1130-1200) and annotations by Ying Huiqian.
The second part discusses the system of musical instruments with the eight sounds of different materials (bayin 八音), and is based on Li Xiangdao's 陳祥道 (1053-1093) book Lishu 禮書 and Li Zhizao's 李之藻 (1565-1630) Pangong liyue shu 頖宮禮樂疏.
In spite of its shortness the book is very reliable in its critical reassessment of ancient writings on music, and helpful concerning the rectification of errors in these texts. It is included in the series Siku quanshu 四庫全書, Siku quanshu zhenben chuji 四庫全書珍本初集 and Baoyishi jikan 寶彝室集刊.