Peking opera was born when the 'Four Great Anhui Troupes' brought Hui opera, or what is now called "Huiju", in 1790 to Beijing, for the eightieth birthday of the Qianlong Emperor on 25 September. It was originally staged for the court and only made available to the public later. In 1828, several famous Hubei troupes arrived in Beijing and performed jointly with Anhui troupes. The combination gradually formed Peking opera's melodies. Peking opera is generally regarded as having fully formed by 1845. Although it is called Peking opera (Beijing theatre style), its origins are in the southern Anhui and eastern Hubei, which share the same dialect of Xiajiang Mandarin (Lower Yangtze Mandarin). Peking opera's two main melodies, "Xipi" and "Erhuang", were derived from Han Opera after about 1750. The tune of Peking opera is extremely similar to that of Han opera, therefore Han opera is widely known as the Mother of Peking opera. "Xipi" literally means 'Skin Puppet Show', referring to the puppet show that originated in Shaanxi province. Chinese puppet shows always involve singing. Much dialogue is also carried out in an archaic form of Mandarin Chinese, in which the Zhongyuan Mandarin dialects of Henan and Shaanxi are closest. This form of Mandarin is recorded in the book "Zhongyuan Yinyun". It also absorbed music from other operas and local "Zhili" musical art forms. Some scholars believe that the "Xipi" musical form was derived from the historic Qinqiang, while many conventions of staging, performance elements, and aesthetic principles were retained from Kunqu, the form that preceded it as court art.