Oh man, the first intermission isn’t for another 10 years and I really have to pee!
From what I’m hearing, long stretches of silence and so on, it sounds like a cop-out after hearing the idea of a 693-year symphony. If they wanted to do it right, though…
Various musicians and conductors would line up for the chance to be part of it. If you’re a violinist, for example, you would be hustled in during a movement that had no violins, and you would play your piece and then be replaced. No individual musician would have to play longer than they’d be expected to for any other concert. (Then they’d give you a T-shirt that says you were in it.) By replacing artists a few at a time, lots of artists would get to play a little bit, and the music would be continuous. Except maybe when they had to switch conductors-- the movements would have to be no more than a few hours long, or maybe the switching of conductors would have to be very precisely timed and the musicians all very good at counting in their heads while this happened. 
Oh, and tickets would be sold in increments of an hour.
The only problem I can see is writing the damned thing, because as someone who has tried to write music (and given up), it strikes me as taking a whole lot longer to write than to hear. 
strikes out the cussword-- no swearing here, right? :smack"
The REALLY experimental part is that a computer would write it. Just program in some rules about harmony, chords, tempos, and such, and attach a printer that loads tractor feed paper by the box.
AND, you attach accoustical sensor to some other computers so they listen to it. These you program with some rules about music appreciation. The higher the song writing computer scores with the appreciating computers, the appreciating computers output a louder synthesized “applause” noise.
Then you put a feedback loop to the writing computer, so it amends its writing rules to garner more appreciation from the listening computers.
In a century or so you might have something listenable.
And a thousand Windows 98s on a thousand Compaqs will someday write Beethoven’s Ninth Symphony…
I don’t think “damned” counts as a cussword anymore, but I do appreciate your concern. It’s always nice to see posters concerned with civility. ;j
Actually, a guy by the name of David Cope writes AI programs that do a purty damn good job at writing music “in the style of”. Anyway, he’s got a bunch of MIDI and mp3 files on his site for those who are curious about the bleeding edge of musical AI.
He doesn’t have the Ninth but there’s a piece that’s very, very close to the moonlight sonata.