What are the deductive forms and outstanding features of Cai Yu in Tang Dynasty?

Jiao Fangji contains 46 great songs, among which Cai Yu is the most famous. "Colorful Feather" is called "Nishang" for short, and the music belongs to the French music in Daqu. The structure of French music is the same as Daqu, and its characteristic is that the tunes and instruments used are more similar to the traditional Han music "Shang Qing Le". Mainly based on Shang tune, the accompaniment instruments are mostly old instruments in the Central Plains, including chimes and chimes. It is said that "there was a French tune in the early Sui Dynasty, and Yueqing was elegant" ("New Tang Book Rites and Music"). In addition, Chen Yun's "Le Shu" records that "Faqu originated in the Tang Dynasty and Nanyin began in Shang Dynasty". "Colorful Feather" music was conceived and created by Xuanzong of the Tang Dynasty, and was partially absorbed by the Indian Sanskrit brought by Yang, and was compiled into a dance "Dancing in Dress and Feather". Bai Juyi's Song of Clothes and Feathers describes this kind of music and dance as "Paixiao, Zheng and Xiao, which are mixed with each other and the sound of playing is abrupt." Six can't play with clothes, and the balcony can't fly. "It can be seen that at first it was a free random sequence. Musical instruments such as Qin, Xiao, Zheng and Di sounded in turn according to the different textures of gold, stone, silk and bamboo, and played several times in this way." Su Yun's Careless Flying shows its beauty, which makes people "love to dress when singing". In the sequential rhythmic dance, "floating around the snow light, I started to send Youlong a surprise. After the small hand, the willow is weak and inclined, Yun Qi. "The initial form of the dance of clothes and feathers is flexible, and its image can be seen in Snow Back and Youlong. The rhythm of Liu Wei and Yun Yu Sheng is really wonderful, and then the next chapter is spread out. " The smoke moth is at a loss, and the wind sleeves are low and affectionate. Shangyuan refers to the green calyx, and the queen mother bid farewell to Joan. "Chen Qing and Fei Qiong are both fairies, and the fairy feelings in" Nishang "are among them. After all these images are full of dance, the people's songs are "broken", and the scene is "twelve voices are urgent, and the pearls are broken." "This is the climax of the dance, full of passion, fast rhythm, complex melody, perfect harmony and forceful. Generally, Daqu ends with a beat, while Nishang ends with a long note. The so-called "Xiang Luan dances with his wings, and the crane song will eventually lead." When Bai Juyi was the general manager of Neo-Confucianism, Zuo Shiyi and a bachelor of Hanlin in Chang 'an during the Yuan Dynasty, he saw the performance of "dancing in clothes" in the palace with his own eyes, and he had the above poem description. No wonder the poet "sang and danced countless times, so he loved the dance in skirts".