What is "demetrio"

Demetrio is an eighteenth-century Italian opera in 3 acts by the Czech composer Josef Mysliveček. It was the composer's first setting of a libretto by the Italian poet Metastasio that was first performed in 1731, one of the most popular of the Metastasian librettos in Mysliveček's day. For a performance in the 1770s, it would only be expected that a libretto of such age would be abbreviated and altered to suit contemporary operatic taste. The cuts and changes in the text made for the 1773 performance of Mysliveček's opera are not attributable. All of Mysliveček's operas are of the serious type in Italian language referred to as opera seria.