Sonata Form
Sonata Analysis Theory Things   William Wieland
(a.k.a. Sonata Allegro Form or First Movement Form — First movements of classical works are often allegro and in sonata form.)

* In minor, the second theme may be in either the relative major (III) or the dominant (V).
The Exposition establishes tonic then modulates to a new key. If the exposition is repeated, a short transition may modulate back to tonic.
  • Theme 1, the first theme or group of themes, grabs attention. It is entirely in tonic.
  • tr, the transition or bridge, modulates to V or V/V (possibly III or V/III in minor). A dependent transition is motivically related to the first theme.
  • Theme 2, the second theme or group of themes, is in the new key and is usually a lyrical contrast to the opening theme(s).
  • A second bridge may link theme 2 and the closing theme.
  • c, the closing theme(s) or codetta, employs cadential figures and confirms the new key.
  • Rtr, the retransition, is an optional bridge-like section which concludes the development by settling on the dominant in anticipation of the return to tonic.
The Development may begin like the exposition (transposed) or with the closing theme or even a new theme in a new key. The development freely manipulates musical ideas (keys, themes, textures, dynamics and even tempos) evoking restlessness, drama, surprise and tense expectancy. The development provides an important contrast to the more direct and stable outer sections.

The Recapitulation is much like the exposition in structure and may employ an identical first theme. However the transition is altered to end on tonic or dominant so the secondary and closing themes confirm tonic.

Keys are as important as themes. Many Haydn sonatas are monothematic, i.e. Theme 1 = Theme 2, transposed.

The exposition is often repeated. The development and recapitulation are sometimes repeated.

Introductions and codas are common.
Beethoven: Sonata op. 14 no. 2 with sonata form explanations (YouTube)