"Never run after a bus or a woman; another will be along shortly" - Evan Esar
***
After listening to a million and one tracks and poking around, this is what I gather is the story of the Requiem for a Dream Two Towers remix (the one used in the second half of the trailer; and why there're so many versions floating around):
About 1 1/2 minutes of music was used in The Two Towers trailer. It was a re-orchestration, with choir, of the Lux Aeterna theme from Requiem for a Dream. This was not released on CD.
People asked for it, so they released 3 samples on tracks on a CD ("Requiem for a Tower"), totalling 2 1/2.
This was where the fun began.
Someone mixed these samples into a 4 minute track.
Someone else then made a 6 1/2 minute track using the 4 minute track, combining it with music from the original soundtrack of Requiem for a Dream, and probably remixed it again too. Which is why you get eerie yowling and the Kronos Quartet at the start of the track, which transitions into orchestral/choral chords later on.
Then someone else also made a 3 1/2 minute track replicating the music from the Two Towers trailer (which incidentally is only 3 minutes)
Which is why you have tons of versions lying around.
Frigid Girl: what thE HELL
the music started playing while d/ling
i was scared
i was wondering how come 'what sweeter music' suddenly sounded demonic