Zaju was a form of Chinese opera which provided entertainment through a synthesis of recitations of prose and poetry, dance, singing, and mime, with a certain emphasis on comedy (or, happy endings). Although with diverse and earlier roots, zaju has particularly been associated with the time of the Yuan dynasty (1271–1368), and zaju remains important in terms of the historical study of the theater arts as well as Classical Chinese literature and poetry. Zaju is known to have been performed during the earlier Song (960–1279) and Jin (1115–1234) dynasties. The various particulars of the zaju multimedia performance were derived from many and diverse sources of musical, dance, poetry, and theater traditions. The Yuan zaju were poetic music dramas comprising four acts, with the "act" (齣, chu) defined as a set of songs following and completing a certain musical modal progression. Occasionally one or two "wedges" (楔子, xiezi), or short interludes in the form of an aria performed by another character might be added to either support or enhance the plot. Within the acts, lyrics were written to accompany existing tunes or set-rhythmic patterns; and, the major singing roles were restricted to one star per act. The zaju featured particular specialized roles for performers, such as dan (female), sheng (male), hua (花, painted-face) and chou (clown). In addition to these main roles there were also a collection of side roles known as 'waijiao' (extra roles) and these consisted of: the jiatou (emperor), the beauty pining in her boudoir, the bawd, the coquettish young girl, the high official, the poor, the brigand, the government servant and those categories concerning immortals and Taoist deliverance, and family matters. On one hand, the zaju theater is the product of a long process of Chinese art, music, and poetry; on the other hand, the zaju also appears as a phenomenon resulting from a combination of cultures of Eurasia over time. Zaju had its genesis even before the Yuan dynasty (1271–1368).