There are different ways to approach operas. There has been many deeply expressive overture, aria and chorus. But over time, a lot of operas come to be known for little more than a single fragment, for example
Hunters' Chrous from Carl Maria von Weber's
Der Freischütz. The the whole opera is much more than that, compelling story, sound effects, etc.
At the end of the day, operas are story telling. From that angle way, opera seria clear has a mind set very different from opera buffa. Compare say, Handel's
Rinaldo to Mozart's
Marriage of Figaro for example. Old opera seria often based on mistaken identity but sometime the plot got twisted so much that heavy handed deus ex machina is needed to close the whole thing off, which could be quite hilarious in modern eyes. Vivaldi's
L'Olimpiade is a good example here. Really catchy overture too.
But, before operas, there were madrigals, cantatas, etc. And a lot more forms before that. I'll post examples in this thread over time, but to get things started, here is a J.S. Bach cantata from his early Mühlhausen days:
Bach: Gottes Zeit ist die allerbeste Zeit (Actus Tragicus), BWV 106
Netherlands Bach Society, Jos van Veldhoven
A masterpiece at many levels. The soprano 'Ja, komm, Herr Jesu!' at
9:12 can be considered the center of the work but one can't just zoom in on it. There is simply no inessential bits anywhere in the whole thing.
