What is the defining characteristic of an opera buffa?

An opera buffa is characterized as a comic opera that typically includes humorous elements, light-hearted plots, and lively characters. This style often contrasts with serious operas, known as opera seria, which focus on dramatic themes and convey elevated emotional content. Opera buffas commonly feature everyday characters and situations, allowing audiences to engage with the narrative in a more relatable and entertaining way.

The emphasis on comedy in opera buffa extends to its musical styles, which incorporate fast-paced, catchy melodies and playful orchestration. Such operas might also include spoken dialogue, contributing further to their comedic effect.

In comparing this with the other options, while mythological themes are often found in more serious works, they don't define the essence of opera buffa. Serious operas are a different genre altogether, focusing on grand and often tragic themes. Instrumental music alone, devoid of vocal elements and storytelling through opera, would not constitute an opera, further distinguishing the opera buffa as a vocal dramatic form.