1. The concerto allowed composers a wide range of flexibility in the manner of treatment. The orchestra could be used simply as an accompanying vehicle, subordinate to the soloist, or they could engage in a free and equal exchange of ideas, a contest between the soloist and orchestra as in the original baroque intent. Likewise, the composer could alternate between the orchestra and soloist in any manner of groupings offering a wide array of textures, colors, and dynamics.
2. Orchestration is important for listeners to consider. A composer can change dynamics simply by reducing or augmenting the orchestration. Point out moments in the Concerto No. 23 where Mozart intensified the dynamics in this way. Likewise, changes in orchestration can provide variety. Consider how Mozart treats the end of the bridge theme in the exposition and compare that with what he does in the recapitulation.