Editing Sonata form (section)

===Coda===
{{Main article|Coda (music)}}
[[File:Mozart- Coda- Sonata in C Major, K. 309, I.png|thumb|upright=1.5|Coda to [[Mozart]]'s [[Piano Sonata No. 7 (Mozart)|Sonata in C Major]], [[Köchel catalogue|K.]] 309, I, mm. 152–155; last bars of recapitulation also presented for context<ref name="B&S"/>{{rp|151}} [[File:Mozart- Coda- Sonata in C Major, K. 309, I.mid]]]]
The coda is optional in Classical-era works, but became essential in many [[Romantic music|Romantic]] works. After the final cadence of the recapitulation, the movement may continue with a coda that will contain material from the movement proper. Codas, when present, vary considerably in length, but like introductions are not generally part of the "argument" of the work in the Classical era. Codas became increasingly important and essential parts of the sonata form in the nineteenth century. The coda often ends with a [[Cadence|perfect authentic cadence]] in the original key. Codas may be quite brief tailpieces, typically in the Classical era, or they may be very long and elaborate. An example of the more extended type is the coda to the first movement of [[Beethoven]]'s [[Eroica Symphony]], and an exceptionally long coda appears at the end of the finale of Beethoven's [[Symphony No. 8 (Beethoven)|Symphony No. 8]].

Explanations for why an extended coda is present vary. One reason may be to omit the repeat of the development and recapitulation sections found in earlier sonata forms of the 18th century. Indeed, Beethoven's extended codas often serve the purpose of further development of thematic material and resolution of ideas left unresolved earlier in the movement. Another role that these codas sometimes serve is to return to the minor mode in minor-key movements where the recapitulation proper concludes in the parallel major, as in the first movements of Beethoven's [[Symphony No. 5 (Beethoven)|Symphony No. 5]] or [[Robert Schumann|Schumann]]'s [[Piano Concerto (Schumann)|Piano Concerto]], or rarely, to restore the home key after an off-tonic recapitulation, such as in the first movements of Brahms's [[Clarinet Quintet (Brahms)|Clarinet Quintet]] and [[Antonín Dvořák|Dvořák]]'s [[New World Symphony|Symphony No. 9]].