How does sonata form create conflict and reconciliation through contrasting keys?

In sonata form, the creation of conflict and its subsequent reconciliation is primarily driven by the manipulation of tonalities, or keys.1

The Exposition: Establishing Conflict

The exposition initiates the movement by grounding the music in the tonic, or "home," key. It then moves decisively to a contrasting, closely related key—typically the dominant in major keys or the relative major in minor keys. This tonal opposition creates a structural tension that defines the movement’s dramatic arc.2

The Development: Dialectical Conflict

In the development section, the musical material is treated dialectically. By modulating through various keys and breaking themes into fragments, the composer subjects the previously established tonal contrast to intense change and conflict.13

The Recapitulation: Reconciliation

The recapitulation serves as the final synthesis. Here, the subjects originally presented in contrasting keys are restated, typically with the second subject now transposed into the tonic key. This return to the home key resolves the tonal tension, bringing the movement into a new state of equilibrium and reconciling the opposites established in the exposition.4