Which genre did Vivaldi NOT compose for?

Vivaldi is renowned for his contributions to the Baroque music genre, particularly through his concertos, sonatas, and orchestral works. While he composed numerous concertos, his most famous work, "The Four Seasons," is a prime example of his concerto form mastery. Additionally, Vivaldi's talent extended to sonatas; he wrote a variety of sonatas for different instruments and ensembles, showcasing his versatility as a composer.

In contrast, quartets were not a prominent genre in Vivaldi's oeuvre, and he did not compose works specifically classified as string quartets in the same way that later composers like Haydn or Mozart did. Thus, "Quartets" stands out as the genre Vivaldi did not focus on, making it the correct answer in this context. While he may have written chamber music that could involve multiple instruments, his specific contributions to the quartet genre are minimal or absent.