Why must counterpoint balance harmony with the independence of each melody?

In the context of counterpoint, the necessity of balancing harmony with melodic independence arises from the dual nature of the technique. Good counterpoint requires both a "vertical" consideration—the harmonious relationship between lines—and a "horizontal" consideration—the individuality of each melodic line.1

This balance is essential because:

• Vertical Harmony: Musical theorists emphasize the vertical aspect, which defines the combination of notes as consonances or dissonances. This ensures the music maintains a meaningful, structured relationship between the simultaneous parts.1
• Horizontal Independence: Composers prioritize the horizontal aspect, focusing on the movement and design of individual lines. Without this independence, the parts would lack the distinct character necessary for true polyphony.1

Ultimately, the art of counterpoint lies in the equilibrium between these two forces. While harmony provides the structural foundation and tension, the independence of each melody allows for the expressive movement and texture that define sophisticated musical composition.12