Task: Question Generation
Input (English): Passage: Monteverdi's next commission from Mantua came early in 1618, when he was asked to provide the music for Andromeda, an opera based on the ancient Greek myth of the princess chained to a rock. The libretto was written by Duke Ferdinando's chancellor, Ercole Marigliani, and the project was sponsored by the duke's younger brother, Don Vincenzo Gonzaga. It is probable that the work was intended for performance at the Mantua Carnival of March 1618, but as Carter records, Monteverdi's approach to his Mantua commissions was often dilatory and half-hearted; his inability or unwillingness to work on Andromeda delayed its performance, first to 1619 and then to 1620.Monteverdi's letters during the 1618–20 period, mainly to Striggio but occasionally to Don Vincenzo or Marigliani, offer various excuses for his lack of progress on Andromeda, including his duties at St Mark's, his health, and his obligations to provide ceremonial music for the Doge (ruler) of Venice. In February 1619, Monteverdi had started work on another Mantuan project, a ballo (dance with sung parts) to Striggio's libretto entitled Apollo. On 9 January 1620, still with 400 lines of the Andromeda libretto to set to music, Monteverdi proposed to Striggio that the entire opera project be abandoned and the ballo substituted. This idea was rapidly quashed; Don Vincenzo ordered that the remaining Andromeda music be sent to him forthwith. The final segment of Andromeda, an eight-part song, was delivered to Marigliani on 15 February 1620.None of Monteverdi's music for Andromeda has survived. The libretto was also thought to have been lost, until its rediscovery in 1984. As was customary in Monteverdi's time, the manuscript makes no mention of the composer's name—librettos were often the subject of numerous settings by different composers. The libretto's frontispiece confirms that Andromeda was performed during Mantua's Carnival, 1–3 March 1620. An analysis of its contents reveals some influence from Rinuccini's libretto for Arianna, such as use of identical metre and length in the prologues of each work, and several common characters in the respective cast lists. The document remains in private hands and has not been published.Monteverdi recorded no apparent interest in the performance of Andromeda after the 1620 Carnival; the long letter that he wrote to Striggio on 13 March 1620 makes no reference to the event and is chiefly concerned with financial matters. The letter implies that the Gonzaga court was trying to persuade Monteverdi to return to Mantua; in courtly language Monteverdi evades the issue, while comparing the relative generosity of his Venetian employers with the parsimony of the Gonzaga court.
Output (English): What are the full names of the two people Monteverdi wrote to only occasionally from 1618-20?