How does a chamber music sonata use a piano and one other instrument?

In the context of chamber music, the role of the piano in a sonata featuring one other instrument has evolved significantly over time.

Before approximately 1750, keyboard instruments like the harpsichord primarily functioned as part of the basso continuo. In this arrangement, the keyboard player improvised harmonies based on a figured-bass line, often supported by a melody instrument like a cello or bassoon to reinforce the bass, while the primary solo instrument played the melody.1

Following the decline of the continuo principle around 1770, the piano assumed a dominant role. In these later sonatas, the keyboard instrument became a self-sufficient partner rather than a mere accompanist. The piano and the solo instrument (such as a violin) engage in a more balanced musical dialogue, often utilizing the sonata form—a structure characterized by the exposition, development, and recapitulation of contrasting melodic ideas. While these works share structural foundations with the string quartet, they are distinct in their specific instrumentation and texture.21