In the second period, guqin music was influenced by Confucian ideology and Daoist philosophy, Central Asian music imported into the imperial court, as well as entertainment music of the Sui and Tang Dynasty. During this period attempts were made to codify playing techniques and notation. Based on the detailed description in the essay "Qin Cao" 【琴操】 by Cai Yong (132–192), the standard form of the qin was most likely set around the late Han Dynasty. The earliest surviving qin in this modern form, preserved in both China and Japan, have been reliably dated to the Tang Dynasty. Many are still playable, the most famous perhaps being the one named "Jiuxiao Huanpei" 《九霄環佩/九霄环佩》, attributed to the famous late Tang Dynasty qin maker Lei Wei (雷威). It is kept in the Palace Museum in Beijing. The earliest known piece of notated guqin music, Jieshi Diao Youlan, dates from this period.