Sonata rondo form

Sonata rondo form is a musical form often used during the Classical music era. As the name implies, it is a blend of sonata form and rondo form.
Structure.
An explanation of sonata rondo form requires first some preliminary coverage of rondo form and sonata form.
Rondo form involves the repeated use of a theme, set in the tonic key, with episodes, each involving a new theme, intervening among the repetitions, like this:
 A B A C A D A ...
Sometimes the A section is varied slightly. The episodes (B, C, D, etc.) are normally in a different key from the tonic.
A sonata form movement is divided into sections.
It may begin with an "introduction", which is commonly slower than the remainder of the movement.
The first compulsory section is the "exposition", whose purpose is to present the movement's main thematic material. This takes the form of one or two themes or theme groups, the second of which is commonly in a related key. This is often the dominant in major-key movements, or the relative major in minor-key movements. The two groups are linked via a modulating transition, or bridge, passage. The exposition may conclude with a short "codetta" and/or closing theme, and may be repeated.
In the succeeding "development" section, existing thematic material may be presented in new harmonic and textural contexts, and/or entirely new material may be introduced.
The development transitions into the "recapitulation", where all themes or theme groups from the exposition are now presented in the tonic key.
 [A B']exp [C"]dev [A B]recap
In the notation, a single prime (') means "in the dominant" and a double prime (") means "in remote keys".
Occasionally, sonata form includes an "episodic development," which uses mostly new thematic material. Two examples are the first movements of Mozart's piano sonata K. 330 and Beethoven's piano sonata Op. 14, no. 1. The episodic development is often the kind of development that is used in sonata rondo form, to which we now turn.
The simplest kind of sonata rondo form is a sonata form that repeats the opening material in the tonic as the beginning of the development section.
 [A B']exp [A C"]dev [A B]recap
By adding in this extra appearance of A, the form reads off as AB'AC"AB, hence the alternation of A with "other" material that characterizes the rondo. Note that if the development is an episodic development, then C" will be new thematic material—thus increasing the resemblance of sonata rondo form to an actual rondo.
The "delayed return" variant in Mozart.
Mozart sometimes used a variant type of sonata rondo form in which the themes of the recapitulation are rearranged: the opening bars reappear quite late, after most of the music of the exposition has been recapitulated, but before the final sequence of themes ("Codetta") that rounds off the section. Thus:
 [A B' Codetta]exp [A C"]dev [B A Codetta]recap
Mozart's purpose was perhaps to create a sense of variety by not having the main theme return at such regular intervals. He used the form in the finales of his piano quartets and a number of his piano concertos.
Codas.
Often, regular sonata form includes a coda:
 [A B']exp [C"]dev [A B]recap [D]coda
This longer version of sonata form has a counterpart in sonata rondo form.
If the coda is arranged to begin with the opening material, then we have yet another instance of A:
 [A B']exp [A C"]dev [A B]recap [A D]coda
Thus: AB'AC"ABAD. An example is the last movement of Beethoven's "Pathetique" Sonata, Op. 13.
Sonata rondo form as a variant of rondo form.
It is also possible to describe sonata rondo form by starting out with rondo form and describing how it is transformed to be more like sonata form. For this explanation, see rondo.
Cuthbert Girdlestone conjectured in his "Mozart and His Piano Concertos" that the sonata rondo form derives also in part from the dances "en rondeau" of Jean-Philippe Rameau, among others, by structural elaboration, possibly an innovation of Mozart's.
Uses of the sonata rondo form.
Sonata rondo form is almost exclusively used in the finales of multi-movement works It is considered a somewhat relaxed and discursive form. Thus, it is unsuited to an opening movement (typically the musically tightest and most intellectually rigorous movement in a Classical work). It is, exceptionally, used in the opening Andante movement of Haydn's D-major piano sonata Hob. XVI:51. Here are some movements written in sonata rondo form: