Why was counterpoint useful for dramatic contrast in Baroque opera and oratorio?

In Baroque opera and oratorio, counterpoint served as a vital tool for creating dramatic contrast by allowing composers to pit different musical forces against one another.1

During the 17th and early 18th centuries, composers utilized a "second practice" of counterpoint that emphasized tone colour and the distinctiveness of individual melodic lines. This technique enabled dramatic tension through several methods:1

• Concerto-like Scoring: Composers contrasted different groups of performers—such as soloists against an orchestra or choirs of voices against instruments—to create a "counterpoint of sonorities".1
• Register and Instrumentation: By using different registers (high vs. low) and varying instrumental or vocal tone colours, melodic lines were made to stand out clearly from one another, such as pitting a soprano voice against male voices and an instrumental basso continuo.1
• Textual Expression: These contrapuntal freedoms allowed for a more expressive treatment of the text, enabling composers to illustrate human character and dramatic themes with greater power.12

By combining these elements, composers like Claudio Monteverdi, Heinrich Schütz, and George Frideric Handel could effectively oppose and combine soloists, ensembles, and instrumental parts to heighten the emotional impact of their works.12