The Sun God is looking forward to the marriage of his granddaughter Medea to Giasone, while Amor is angry because he long ago united Giasone with Isifile. Hercules, for his part, is angry with Giasone because his thoughts are occupied more by Medea than by his quest to find the Golden Fleece. As for Medea, she is happy to be with Giasone and pays no attention to the whining of Egeo, who is in love with her. She is prepared to help Giasone find the Golden Fleece and uses her magical powers to invoke the spirits of hell so that they persuade Pluto to enable Giasone to slay the dragons that guard the Fleece. Oreste was sent out by Isifile to look for her betrothed, but he now has to report to her that Giasone intends to marry Medea. This gives Oreste hope, since he himself is in love with Isifile, but Isifile is thinking only of vengeance. Giasone succeeds in stealing the Golden Fleece from the altar of Giove with the aid of Medea and Pluto, but he and Medea are forced to flee from the irate people. Jupiter is also furious at the outrage committed at his altar, and causes Giasone’s ship to drift to Isifile’s land and then capsize. There the two rivals encounter one another. Giasone pretends to promise to stay with Isifile and marry her. In reality, however, he has, at the behest of Medea, given his loyal captain the order to kill Isifile. Egeo, who has followed Giasone and Medea, suddenly hears the latter crying for help: the captain, mistaking her for Isifile, has thrown her over the cliffs into the sea. Egeo succeeds in rescuing Medea who gratefully embraces him and puts aside her differences with him. However, she demands that he kill Giasone. Giasone, plagued by feelings of guilt, has fallen asleep. Egeo is about to kill him, but Isifile is able to stop him at the last moment. But because Egeo manages to escape undetected, Giasone thinks it was she who attacked him. But now Medea appears and commands Giasone to return to his betrothed whom, in reality, he still loves. When Giasone takes his old beloved in a tender embrace all the gods are content since all the couples that Amor had decreed should be united are now together.
Francesco Cavalli (1602–76) is one of the first to devote himself to the new genre of opera in Venice, which he does with unflagging energy. It is in Venice, the cosmopolitan city in the republic on the Adriatic, that opera first becomes a popular art form thanks to the enthusiasm of every section of the population that can afford to attend. In this way, the central art form of the Baroque age emerges from scholarly experiments and courtly amusements. Cavalli builds on Monteverdi’s style with extraordinary melodic richness. In Giasone we already find all the familiar components of Venetian opera that later takes on so many different facets and is characterised by a careful balance between serious and comic scenes in which eloquent recitatives alternate with catchy songs designed to achieve popular appeal. We find an apparently chaotic assemblage of disparate themes and styles which, however, are perfectly balanced; we find a host of wildly diverse characters from every section of the population; and we are confronted by unexpected switches from the tragic to the comic that leave us open-mouthed and our heads spinning. All this, however, also made Giasone a favourite target for the conservative Accademia dell’Arcadia who declared the work symbolic of “Venetian decadence”. Giasone was first performed in 1649 at the Teatro S. Cassiano. This theatre, opened in 1637, is regarded as the first opera house in Venice to be open to the public. In the space of only a few years the new opera became one of the most frequently performed works of the 17th century: it was successfully staged in virtually every sizeable town in Italy. The eponymous hero is, of course, none other than Jason from the saga of the Argonauts who, with Medea’s help, steals the Golden Fleece. But Cavalli and his librettist Cicognini took a maverick approach to the ancient saga, cheerfully adapting it to their own ends: during the carnival season, audiences expected earthy entertainment, not blood-soaked tragedies, and a lieto fine, a happy ending, was also a must. So this version of the Argonaut saga has a surprising and unusually happy ending with several rather unlikely couples.