Another ducal marriage, that of Francesco Gonzaga, son of the Duke of Mantua, brought to Rinuccini the command to write a new libretto. The poet, full of inspiration, produced two texts, one of which, "Arianna," was composed by Monteverde and achieved great success. The Duke of Mantua then proved to be the general protector of the new art, for we note that he commanded Monteverde to write operas for different occasions. "Orfeo" (1608), "Combattimento di Tancredi" (1613), "Le nozze d' Enea," "Il Ritorno d' Ulisse" are all occasional works of the great reformer. Monteverde died in 1643, and was buried in the Chiesa dei Frari.
The great success of Monteverde's works turned the tide of composition towards the creation of operas, and the popularity of these productions soon suggested the desirability of erecting theatres which should be chiefly devoted to the presentation of opera. The first opera house was built in Venice in 1637, and was called the Teatro di San Cassiano. The owners of it were Benedetto Ferrari and Francesco Mannelli, who wrote respectively the libretti and the music to the first two operas represented there. Francesco Cavalli, Monteverde's favorite pupil, also composed operas for this theatre. Two other opera houses were built at Venice within a short space of time. For these theatres operatic novelties were supplied in rapid succession. The names of the composers were Carlo Pallavicini, D. Giovanni Legrenzi, Antonio Sartorio, and Marc Antonio Cesti. Cavalli was a very prolific writer, having composed between 1639 and 1665 not less than thirty-four operas. The best among them were "Il Giasone" (1649) and "L' Erismera" (1665), of which the manuscripts are preserved in the library of St. Mark at Venice. Legrenzi wrote seventeen operas, the most successful being "Achille in Scyro" (1664) and "I due Cesari" (1683). Opera became more and more fashionable; and, as Venice was one of the greatest musical centres as well as one of the most popular pleasure resorts, the city of the laguna possessed, before the end of the seventeenth century, no less than eleven opera houses, all of which were filled to overflowing whenever performances were given. In Rome, the first opera house, known as the "Torre di Nona," was opened in 1671 with Cavalli's "Giasone"; the second, "La scala dei Signori Capranica," was inaugurated in 1679. A third theatre was that of the Palazzo Alberti (1696.)