I'll dig around. There is a little bit about it in the Pakula bio, I think, and probably in one or two books on cinematographers I have someplace. Might take a couple days though.
Along with Kaufman's BODY SNATCHERS remake, PARALLAX is my favorite 70s political paranoia flick, and the compositional elements, especially in the last reel, are just awesome, in terms of monolithic structures dwarfing the lead.
The one '?' aspect is that the music is exactly what is used in MARATHON MAN when Scheider gets killed ... goes to show that James Horner isn't the only composer who recycles like mad (though nobody gets away with delivering the same thing over & over again like he does, even when he is delivering another composer's stuff.)