How did Vivaldi create contrast in The Four Seasons? adding vocal parts using different themes changing keys frequently adding sound effects

He used different themes throughout

Explanation:

In listening to the excerpts, Vivaldi did not have any vocals or sound effects in The Four Seasons. He did use different themes throughout and depending on which section of the music, keys were changed. However, it seems each theme (Spring, Summer, Autumn, and Winter) were each in its own key, so I believe the answer is using different themes.

He used different themes