1740–1770
After peaking during the 1750s, the popularity of the Metastasian model began to wane. New trends, popularized by composers such as Niccolò Jommelli and Tommaso Traetta, began to seep into opera seria. The Italianate pattern of alternating, sharply-contrasted recitative and aria began to give way to ideas from the French operatic tradition. Jommelli's works from 1740 onwards increasingly favored accompanied recitative and greater dynamic contrast, as well as a more prominent role for the orchestra while limiting virtuosic vocal displays. Traetta reintroduced the ballet in his operas and restored the tragic, melodramatic endings of classical dramas. His operas, particularly after 1760, also gave a larger role to the chorus.
The culmination of these reforms arrived in the operas of Christoph Willibald Gluck. Beginning with Orfeo ed Euridice, Gluck drastically cut back on the possibilities for vocal virtuosity afforded to singers, abolished secco recitative (thereby heavily reducing the delineation between aria and recitative), and took great care to unify drama, dance, music, and theatrical practice in the synthesis of Italian and French traditions. He continued his reform with Alceste and Paride ed Elena. Gluck paid great attention to orchestration and considerably increased the role of the chorus: he also cut back heavily on exit arias. The labyrinthine subplots that had riddled earlier baroque opera were eliminated. In 1768, the year after Gluck's Alceste, Jommelli and his librettist Verazi produced Fetonte. Ensemble and chorus are predominant: the usual number of exit arias slashed in half. For the most part, however, these trends did not become mainstream until the 1790s, and the Metastasian model continued to dominate.
Read more about this topic: Opera Seria