Conversation so far:
who plays the contrasting sections in a ritornello
In the Concerto Grosso, a ritornello structure was used, in which a recurrent section, or ritornello, alternates with episodes, or contrasting sections, played by the soloists.
In what kind of music are the ritornellos played
A ritornello is a recurring passage in Baroque music
What is the meaning of Baroque
The word “baroque” comes from the Portuguese word barroco meaning misshapen pearl

Question: In what period
Self-contained rewrite: In what period was Baroque music first composed