How did concerto style create counterpoint through contrasting groups of performers?

In the context of the Baroque concerto, the style created a unique form of counterpoint by emphasizing the opposition and interplay between contrasting groups of performers, specifically the full orchestra (tutti or ripieno) and the smaller solo group (concertino or soli).12

This approach, often referred to as the stile concertato or concerted style, utilized several methods to generate contrapuntal interest through these contrasting masses of sound:

• Sonority and Tone Colour: By pitting groups of different sizes and instrumental timbres against one another, composers achieved a "counterpoint of contrasting sonorities." This expanded upon earlier Renaissance techniques where choirs of voices or instruments were set off against each other.2
• Motivic Interplay: Beyond simple alternation, the style featured imitative interplay between the tutti and soli choirs. This involved the exchange of musical themes and figures, creating a texture of interwoven melodies that functioned contrapuntally.1
• Dynamic and Rhythmic Contrast: The opposition between the "weighty" tutti and "light" soli allowed for sharp contrasts in dynamics and rhythmic complexity. The soli were often assigned more intricate, virtuosic passagework, while the tutti provided steady, solid beats, creating a dialogue that defined the concerto’s structure.12

Ultimately, this style allowed composers to integrate dramatic contrasts into instrumental music, culminating in works like J.S. Bach’s Brandenburg Concertos, which masterfully fused contrapuntal lines with these distinct instrumental colors.2