It might be best to listen before reading all this crazy stuff.

rather mathematical this one

it started with the title

that led to the idea of an endlessly descending 12-tone scale. the scale starts at Ab

that led to a chord progression with a 10 beat length. the chords are: E G B C# E B Asus4 A C G

each time the chords repeat they start 2 half-steps up from before

picked out the notes from the chords that persisted for 2 or 3 beats as the primary notes for the main melody line

built a 20 beat melody constrained to only using notes directly from the chords, and being sure to not reuse notes from the first half in the second half (important in a moment)

built a second 10 beat melody made up of the left-over notes from the chords not used by either the first or second half of the 20 beat melody

then arranging proceeded from these elements

the whole song is built of repeated playing of the 10 beat cycle. every 6 times around is 60 beats. the endless scale (12 beats) fits in there exactly 5 times

started with piano playing portions of the chords building to playing them fully

then the flute plays the 10 beat melody through a full-circle of 5 repeats

the percussion comes in to help the listener stay oriented as more elements enter (also, the gong introduces each of the changes coming up)

an oboe then echoes the full-circle

next, the french horns play the 20 beat melody for a full-circle

10 beats into the second repeat of the full-circle, a second section of horns come in again suitably modulated (up 2)

the melody is a round due to its construction from notes only from the chords, and is a counterpoint of the 10 beat melody as well

then the voices sing the chords for a full-circle

finally, the endless scale slowly fades in, as all the rest fall away

and the endless scale fades out

here's a chart that might help
https://web.archive.org/web/20151003080054im_/http://home.comcast.net/~t129wojce647/music/tunes/falling_chart.gif