From what I can figure out from the Reason patch (I attached a screenshot), it is using waveform 13 (a "harmonically rich waveform suited for organ sounds"), which I am using a low-passed saw to approximate.
It is then going through a noise-based LFO (which I am using a [noise~] going through a [sah~] to be able to vary the "rate" of the noise) which is modulating the "mix" of the sound (ring modulation).
It is finally going through a lowpass filter modulated by an envelope.
I threw together a crappy patch in the 15 minutes on my train ride based on the Reason patch. It sucks but I think that someone on here could run with it.
It is possible, and not that difficult to do sound design in Max. I don’t claim to be an expert.
One last thing. [bp~] in Pd has a "Q" value which can be greater than 1 but in Max, [svf~]’s Q value must be between 0. and 1.