Howdy, so David, kinda getting back from my break, thought I'd have anohter look at this...
Seems the extended object is related to the 2004 Huovalainen paper, but I've failed to fully understand the code of moog.c and really match them.
Anyone knows about Gunter's wherabouts these days? He could give us a hint. And yeah, I also saw some moog filter by Miller, which I should find back and check as well...
Here's another cool thing I found on the web.
So, by looking at the Huovalainen paper, seems doable to do it with [fexpr~]. In the end, it's just some 4th order filter, right?
Have you checked MoogFF in Supercollider?
cheers