Show off your theory chops with my weekly challenge! You’ll find a new question here every Monday. Please comment to post your reply.
This week’s challenge:
Sonata form is the name we give to the structure of many symphonic first movements. In modern times it’s often thought of as ternary (or three-part) form: exposition–development–recapitulation. However, even in the late symphonies of Mozart, you’ll find a repeat sign at the end of the recapitulation, going all the way back to the start of the development. What does this reveal about the origins of sonata form?

Reply to post your answer, and check back on Friday, December 10th to see if you’re right!
ANSWER for 12/6/21
Well done everyone! Sonata form was a development (pun intended) of rounded binary form:

Renaissance dance forms became adapted into Baroque instrumental movements, particularly binary form with repeats on each section. Rounded binary had the A material return after the B section. As time went on, it became standard practice for the first A section to modulate, often ending in the key of V. However, when the A material returned after the B section, it reasserted the tonic key, rather than modulating. The B section became an episode in which the themes “exposed” in the A section could be developed; hence the modern terms “exposition” and “development.”
By the early 19th Century, composers began to see a more linear narrative in this form. To that end, Beethoven was one of the first to do away with the repeats on either side of the B-A section. This was an important step toward the evolution of sonata form into a more programmatic drama, or, at least, a structure with extramusical implications. An operatic parallel can be found in the reforms of Gluck, who felt that the da capo aria’s repeat was a purely musical convention that hindered the dramatic narrative.
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