It’s an old article, but very fascinating. Jan Swafford in Slate:
[T]he Ninth has attained the kind of ubiquity that threatens to gut any artwork. Think Mona Lisa. Still, as with Lisa, when that kind of success persists through the centuries, there are reasons.
One reason is its mystery. Figuratively speaking, everybody knows the Ninth. But has anybody really understood it? The harder you look, the odder it gets. In a singular way, the Ninth enfolds the apparently contradictory qualities of the epic and the slippery.
First movement: loud, big, heroic, no? No. Big and loud all right, also wildly unstable, searching, inconclusive—everything heroes aren’t. The formal outline, on the surface a conventional sonata form, is turned inside-out: The development section in the middle, usually a point of maximum tension and drama, is the relatively most placid part of the movement; the recap, the return of the opening theme and usually elaborately prepared, erupts out of calm like a scream, with a major chord that somehow sounds hair-raising. (Major keys and harmonies being traditionally nice, hopeful, that sort of thing, minor ones darker, sadder, etc.) At the end there’s a funeral march over a slithering bass. Beethoven wrote funeral marches earlier, one the second movement of the “Eroica” Symphony. There we can imagine who died: the hero, or soldiers in battle. But who died in the first movement of the Ninth?
Next comes the scherzo, Beethoven’s trademark skittering, ebullient movement. Here it’s those things ratcheted up to a Dionysian whirlwind, manically contrapuntal, punctuated with timpani crashes. Strange choice, to follow a funeral march.