I think you might be right...i've been doing some research and i think it's GRM tools, which make vowel sounds in combination with a synth, but I can't use it with REASON, so I will never know for sure.
if he used the subtractor, i think it might be using a combination of the two lfo's, and setting the synch rate at about 1/4 on the first one, and then modifying the second lfo to taste. I think combining different wave forms will allow you to get your individual sound, but i think a square and a triangle, or sine work pretty well together. I've seen a lot of people saying that they use triangles only for this type of sound, but judging by different producers, they experiment with way more than just triangles. I was messin around last night for a couple hours, and trial and error really get you close to that sound, but you'll NEVER sound exactly like another producer, so don't feel like you're coming up short.
you might wanna expand on your repitoir <?(spelling) of synths, ive tried makin sounds like that in some synths and get no where near, go through the same procedures in the tone 2 firebird or toxic 3 and its right on the money, every synth has its own sound so to speak even if u create the same set of paramaters they can sound very different, so shop around, id advise the toxic 3 or firebird cus theyre just so unbelievably sik, but yeah with that sound in particular it could be a vocoder like people bin sayin, just record yourself goin 'wuahhhh', but it sounds to me like the vocal filter in the firebird or gladiator by the same company, bit of tweakin on the amp and filter envelopes with some dirty saw's n tri's i dont think ull be far off tbh
No idea about how to do it with Subtractor (clever filter automation I reckon), but do it with Thor instead and use the formant filter - you'll make the job a hellova lot easier. (Assuming you're on Reason 4)