Considering, that he was hearing all he was coming up with, without the influences of radio, T.V., et al....such as we have now....I personally think, and its only an OPINION, that he was tapped into something, other than pure mechanics...However, that being said, the Fifth, is extremely mechanical in structure..arrangement-wise, is something else. ....but then his piano concertos, are definitely, inspired, and in turn still inspire!

GfS