I was just trying to program this on my Deepmind12 yesterday. Googled and found the Keyboard article. Spent some time and got close, but still no cigar. If you're reading this, Burningbusch, would love to get schooled!!
EDIT: Was failing to get that "hollow" sound and the right kind of modulation, but getting much closer after a session today.
For me, the feature that nailed the sound was the downward pitch on the attack. Listen to As Falls Wichita... "It's for you" (Which is the motivation for the the Album cover).
On "It's for you", the organ chord on the end of the vocal interlude is the most exquisite polychords I've ever heard!