Italian opera seria (invariably to Italian librettos) was produced not only in Italy but also in Habsburg Austria, England, Dresden and other German states, even in Spain, and other countries. Only France had its own distinct operatic tradition.
More than anyone else's, the dramatic conventions expressed by the librettos of Metastasio crystallized the format of opera seria. In 1722 Pietro Trapassi, called Metastasio, a brilliant and personable young poet, was called upon to supply a libretto as part of the festivities for the Empress of Austria's birthday. The piece was termed a 'serenata' (literally an 'evening's entertainment') but it was less like what we would recognize as a musical serenade and more in the tradition of the court masque. It was titled Gli Orti Esperidi, 'The Gardens of the Hesperides'. Nicola Porpora, (much later to be Haydn's master), set it to music, and the success was so great that the famed Roman prima donna, Marianna Bulgarelli, 'La Romanina,' sought out Metastasio, and took him on as her protegé. In La Romanina's household. Metastasio took music lessons and met all the leading composers.
Under her wing, Metastasio produced libretto after libretto, and they were rapidly set by the greatest composers in Italy and Austria, establishing the transnational tone of opera seria: Didone abbandonata, Catone in Utica, Ezio, Alessandro nell' Indie, Semiramide riconosciuta, Siroe and Artaserse. After 1730 he was settled in Vienna and turned out more librettos for the imperial theater, until the mid 1740s: Adriano, Demetrio, Issipile, Demofoonte, Olimpiade, La Clemenza di Tito, Achille in Sciro, Temistocle, Il Re Pastore and his greatest libretto, Attilio Regolo. For the librettos, Metastasio and his imitators customarily drew on dramas featuring classical characters from antiquity bestowed with princely values and morality, struggling with conflicts between love, honour and duty, in elegant and ornate language. Useful stylistic comparisons with the High Baroque operas of the 17th century may find parallels in contemporary Late Baroque architecture: academic, more disciplined, self-consciously classicizing, a contrast between the High Baroque of Bernini and the Late Baroque of Jules Hardouin Mansart.
Opera seria built upon the strict dramma per musica ('drama through music') conventions of the High Baroque era by developing and exploiting the da capo aria, with its A-B-A form. The first section presented a theme, the second a complementary one, and the third a repeat of the first with ornamentation and elaboration of the music by the singer.
A typical opera would start with an instrumental overture of three movements (fast-slow-fast) and then a series of recitatives containing dialogue interspersed with arias expressing the emotions of the character. After an aria was sung, the character usually exited the stage, encouraging the audience to applaud. This continued for three acts before being concluded with an upbeat chorus or duet. The leading singers each expected their far share of arias of varied mood, sad, angry, heroic or meditative.
The age of opera seria corresponded with the rise to prominence of the castrati, prodigiously gifted singers with high, powerful soprano voices backed by decades of rigorous musical training. They were cast in heroic male roles, alongside another new breed of operatic creature, the prima donna. The rise of these star singers with formidable technical skills spurred composers to write increasingly complex vocal music, and many operas of the time were written as vehicles for specific singers, of whom the most famous is perhaps Farinelli, whose debut in 1722, guided by Porpora, coincided with the arrival of opera seria itself..
Given the extensive stylistic conventions of opera seria, it was a considerable challenge to write an effective drama, and not surprisingly many opera seria consisted of little more than cardboard characters and vocal exhibitionism. However, several composers transcended the genre, most important of whom was the Prussian George Friderich Handel (1685 – 1759), who wrote some fifty operas, mostly for the theaters of London, where he spent most of his career. More famous than Handel in their lifetimes, however was Johann Adolph Hasse (1699 - 1783).
While obeying the conventions of opera seria, Handel developed real flesh-and-blood characters, thanks to his prodigious lyrical and dramatic gifts. But after Handel's death tastes changed, and his operas fell into obscurity, save the odd fragment, such as the ubiquitous larghetto from Serse, "Ombra mai fù", his most famous melodic structure.
However, beginning in the 1960s, the revival of interest in baroque music and original instrument playing styles, the development of the countertenor fach, and popularity of the long-playing record made rediscovery of Handel's Italian operas possible, and many have since been recorded and performed onstage. Of the fifty he wrote between 1705 and 1738, Alcina (1735), Ariodante (1735), Orlando (1733), Rinaldo (1711,1731), Rodelinda (1725), and Serse (also known as Xerxes) (1738) stand out and are now performed regularly in opera houses and concert halls. His finest work however is Giulio Cesare (1724), a tour de force of superb vocal and orchestral writing, possibly the finest opera seria of all.
Wolfgang Amadeus Mozart (1756 –1791) was Handel's most direct descendant in the lineage of opera seria. His two notable contributions to the genre are Idomeneo (1780) and La Clemenza di Tito (1791). For most of the 19th and early 20th century both operas were virtually unknown, but starting in the 1960s, the two slowly regained a place in the standard operatic repertoire. Mozart wrote some beautiful music for these operas, but the characters, drawn from classical antiquity in accordance with the conventions of the genre, did not inspire in him the same level of incandescent musical theater as the three operas to more modern librettos by Lorenzo da Ponte.
Other notable contributors to the opera seria genre were Christoph Willibald Gluck (1714 – 1787), Luigi Cherubini (1760 – 1842), and Gaspare Spontini (1774 – 1851). Gluck tried to reform opera seria by reinstating the supremacy of the drama over the singers; he also did away with the recitative. Cherubini and Spontini expanded upon his ideas. Greatly admired by fellow composers such as Beethoven and Berlioz, the three enjoyed greater critical acclaim than popular success, and following the Napoleonic era, when the brilliant, effervescent operas of Rossini swept the continent with their vocal pyrotechnics, their classically austere operas fell out of fashion. But even Rossini set Metastasio's libretti to the new music.