Piano Sonata no. 15 in D major Op. 28 third movement
This A section is clearly marked out by the structural phenomena of the double bar between measures 32 and 33. This A section is constructed of four, eight measure phrases. These phrases are alternating back and forth from original D major to it’s dominate A major. In measure 8 we have a PAC in D major. In Measure 16 we have a PAC in A major. Then, again in measure 24 we have a PAC in D major, and then in measure 32 we have a PAC in A major. At this point, this is where we see the double bar line. We do not repeat the A section at this time. Besides the double bar line, the only other structural phenomena are dynamic shifts in measures 17-20 and then again in measures 25-28. The rhythms, textures, meter, and everything else remain the same. I would say this section is expository and continuous because it ends in the dominant key. The periods are symmetrical, and parallel.
The B section begins after the double bar line and right away has a dynamic change, texture, and density change because the notes are being held longer. This next part I would consider as a transitory section. It feels as though it is just trying to work us back to the original key, which it does finally at measure 49. At this point the A section is reintroduced. As it goes along it gains more texture and a dynamic change in measure 57 becoming more of a developmental A section. Right before in measure 56 there is a cadence of a PAC in D major. This developmental section ends in measure 68 in the original key of D major on a PAC so that it would make it rounded binary form.