[sdiy] Envelope follower/Zappa question

[synth at oldmail.charlielamm.com]

One of my all time favorite guitar solos is Frank Zappa's "Penguin in
Bondage", from "Roxy and Elsewhere" Album (which has a lot of killer
playing on it BTW!)  One reason I have been building env. followers is to
try to nail that sound....being unable to find a stomp that can recreate 
it.

It sounds to me like Zappa uses an envelope follower on that solo, but, I
never have been able to recreate it, or even come very close. It sounds
like a lowpass filter with some resonance, and some very odd tracking of
the attacks of his playing. It's awesome! It's gonzo! It kills! Does
anyone know how he got it?

Note: I had heard at one point he was processing his guitar through an Emu
modular.....not sure if he was doing this way back then though.

Thanks in advance.  

--CL