Zhonglü tongkao 鐘律通考 "Thorough investigation of the bell bitchpipes" is a book on musical tuning written during the Ming period 明 (1368-1644) by Ni Fu 倪複, courtesy name Ruxin 汝新, who hailed from Yinxian 鄞縣 (modern Ningbo 寧波, Zhejiang).
His book of 6 juan is divided into 27 chapters that describe all matters of music from a description of the twelve pitch pipes to concrete melodies to songs from the Confucian Classic Shijing 詩經 "Book of Songs". The arrangement of the book is not done very well, and it might be that copyists are responsible for inconsistencies in the presentation of chapters. The book is accompanied by a preface written by Zhang Bangqi 張邦奇 (1484-1544) in 1526, where it is said that the author relied largely on the rules and customs transmitted from the past.
Yet is can be seen that in many points the quotations in the Zhonglü tongkao deviate from the original texts, be it statements in Cai Yuanding's 蔡元定 (1135-1198) book Lülü xinshu 律呂新書, or the great Neo-Confucian master Zhu Xi 朱熹 (1130-1200). In spite of all these consistencies, the book is included in the imperial series Siku quanshu 四庫全書.