What are the elements of the Classical Sonata Form?

The Classical Sonata Form has three main sections. First is the Exposition. This introduces the main two themes of the piece. The first theme is in the tonic key, and the second theme is usually either in the dominant or relative minor key. The second section is the Development. In this section, the main themes are developed further. This section usually modulates do different keys. The third section is the Recapitulation. This uses the two main themes again, however both are in the tonic this time. There are usually a few differences in instrumentation here and it is normally shorter than the exposition.