Anders, my argument was not based on the upbeat being the dominant, but on the motivic use of this particular upbeat C, especially since it forms the basis for the long transition before the recapitulation. Making much out of little was Beethoven's speciality, and as a special feature of this particular work, I think this relationship deserves to be brought out in performance. I think that this is the kind of insight that will bring a performance to life. Beethoven's inexhaustible imagination makes every work he created a special case, and I think each has to be dealt with that way.
In any case, for me, generalities about style count for less than the special features of a specific work. For that reason, I trust what Beethoven actually wrote (and I don’t mean merely the surface details) over current ideas about what constitutes “correct” style, which tend to change according to fashion:
For example, at one point, many were convinced that several generations of musicians had been playing J. S. Bach’s trills incorrectly, and that they should all start on the beat and with the upper note. They could point to a lot of historical data to prove it. Then, a few courageous souls (most notably F. Neumann) showed through internal evidence that this produced absurd results in many cases, so that it seemed far more likely that the performance of every one of Bach’s ornaments is context-driven and must be played according to good musical sense, which was exactly what many musicians had been doing all along before and after the trill dogma struck.
To try to make my original case more focused, I didn't mention another important use of the opening note at the very beginning of the piece, but will do so here, since it has some bearing on my point as well as explaining why I think the C upbeat deserves special treatment:
Note how the C upbeat provides the springboard for each of the following short phrases, which have as their goals A-flat, then B-flat, then a restart on A-flat, then again B-flat and finally to the main goal note C. The whole larger phrase constitutes the melodic progression A-flat, B-flat, C.
Understanding the function of the C as an upbeat launcher also suggests starting the appoggiaturas and the rolled chord before the beat, in contradiction to what many might feel is “correct” Classical style. But for me, since we don’t really know how Beethoven played these ornaments, what is actually in this one specific piece of music is more convincing basis for a performance than generalities about what we think "they" might have done back then, based only on secondary evidence.
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