Sonatas may optionally end with a final large section called the coda.
Occasionally, sonata form includes an "episodic development," which uses mostly new thematic material.
By adding in these extra appearances of A, the form reads off as AB'AC"ABA, hence the alternation of A with "other" material that characterizes the rondo.
Mozart sometimes used a variant type of sonata rondo form in which the first "A" section of the recapitulation is omitted.
Thus: Mozart's purpose was perhaps to create a sense of variety by not having the main theme return at such regular intervals.
Another six-part sonata rondo form may be written as: This instance occurs in the 4th movement of Tchaikovsky's Symphony No.
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.
It is, exceptionally, used in the opening Andante movement of Haydn's D-major piano sonata Hob.