Beethoven was facing an especially tough compositional problem. He’d just brought off one of the most singular coups in music. The problem was how to repeat it.
A little context: The third movement of Beethoven's Fifth Symphony is that mischievous descendant of the minuet known as a scherzo (Italian for "joke"); the symphony's fourth movement is a rousing finale. This sequence of symphonic movements is entirely conventional (Haydn had patented it decades earlier). But in the course of the 5th's scherzo, some strangeness starts seeping in. The movement begins with a quiet theme, followed by a loud one whose da-da-da-DAH rhythm echoes the famous “fate” motive that opens the symphony. (This stentorian theme comes in at 0:21 in this clip.) In a typical scherzo, these themes would, after an intervening episode, be literally repeated. Sure enough, the quiet theme does return (at 3:14), but–the first hint that something unusual is up–after a few measures, Beethoven reorchestrates it (bowed notes become plucked ones). And when the loud theme returns as expected (at 3:35), it isn’t loud: it’s as quiet as the quiet theme–and also reorchestrated (stated not by the horns of its first appearance, but by more plucked notes in the strings ).
As if these departures from the norm weren't peculiar enough, at the point where the movement should end, it doesn’t. It’s suspensively prolonged (starting at 4:46) by a sustained low note which is soon joined by wisps of the scherzo's "quiet" theme. Things are clearly hanging some sort of fire…until without warning a rapid build begins, a breathless crescendo that climaxes in the fortissimo opening theme–all golden trumpets and sun-resplendent C major–of the fourth movement (at–not that you could miss it–5:07). This glorious outburst, we realize in retrospect, is what Beethoven has been setting up with all the unwonted quiet that's been preceeding it.
So far, so stupendous. We're now into the symphony’s final movement. This movement is in a classical finale's usual “sonata form.” An all-but-mandatory feature of a sonata-form movement is a return, part-way through, of its opening theme. And with this requirement comes Beethoven’s above-mentioned problem. After all, the original statement of the finale's opening theme was so stunning that its return will almost have to be a letdown. But what made this theme’s original statement so stunning? The suspensive buildup to it. Of course that buildup, being a feature of the preceding movement, is now history... Whereupon Beethoven issues one of the great “So what?”‘s in the history of the arts. If the buildup to the finale's opening theme was essential to that theme’s impact, then let's bring the buildup back! Let's just forklift the whole bleeping buildup out of third movement into the fourth! Which Beethoven goes ahead and does (at 8:39)--resulting in a return of the finale's opening theme (at 9:21) that has all the splendor of its original appearance. The boldness, even ruthlessness, of this solution reminds me of a method suggested, when all else fails, for dealing with a bottle of beer that's proving hard to open: bite the end off it.