The sonata form.
In particular, the sonata form typically was the structure of the first movement of classical symphonies. Sonata form follows this pattern:
Exposition: Two musical themes are set forth or "exposed" to the listeners. (Thus the label "exposition.") The first theme is usually strong, the second quieter, more gentle.
Development: Then the two themes are explored or "developed" in various ways and played off of one another.
Recapitulation: Finally, the themes are restated in the order in which they were introduced in the exposition section and reaffirmed as the musical themes of the movement.
