What denotes the theme in the exposition section of sonata form?

In the exposition section of sonata form, the primary function is to introduce the main themes of the piece. This section typically presents two contrasting themes, often in different keys. By doing so, it establishes the musical ideas that will be developed and transformed in later sections of the sonata form, such as the development and recapitulation.

The focus on introducing these themes is crucial because it sets the stage for the overall structure of the composition. Understanding this part of the sonata form is essential, as it lays the groundwork for the listener's experience and the subsequent musical dialogue. The other options describe processes or features that occur in different sections of sonata form, but the primary goal of the exposition is to clearly present the themes for the first time.