Beethoven's Opus Posthumous definitely carries a slight weight of confusion concerning it's correct form. The argument is whether to conceive this piece as a five-part rondo, seven-part rondo, or a ternary composite. Yes, many choices, but only one decision can be made. However, this proves a difficult task considering this piece has musical aspects that pertains to each of the three previously listed forms.
Personally, I believe this piece to be a five part rondo due to the overall form, ABACA. Where is the primary confusion?
Like any ordinary five-part rondo, it begins with it's refrain, A. It's set in the key of F major and ends on a PAC. This leads right into the B section. Nothing quite out of the ordinary yet. We then view a transition back into the refrain, or A2. A2 ends on a PAC, and then enters the C section, which happens to be in the key of vi, or D minor. This section creates the most confusion. Moving into a the key of vi is primarily a seven-part rondo characteristic. Another confusion that approaches the listener is the length and the discontinuity of the section. However, I bellieve the second section of C is basically a continuation of the section, but portrays differences. Lastly, there is a retransition back into the key of F Major.
Of course, as the book suggests, a little more analization reveals another type of breakdown. When splitting this piece into each of it's sections, each comes out as a rounded binary form. And when a piece contains a mixture of forms it is known as composite ternary. However, the continuous return to A solidifies the notion of a rondo.
Lastly, there is a differnce concerning phrase rhythm between the sections. A has a standard eight-measure rhythm, that complies with a standard period. However, sections B and C vary. Section B is a ten measure phrase. While section C contains a main period that continues for 11 measure. This creates a sense of hypermeter in the piece. Once again, it brings out the unusual characteristics of the piece and just leads the listener to more confusion. However, I don't think there is anything to be quite confused about. I believe Beethoven prepares his audience for variety in his piece by choosing unusual chord progressions in A.