Since
the low pass-ness is created with a Vactrol, you get a spongy-boingy
sound that's very characteristic.
As I read this, it occurred to me that vactrols might be responsible for the interesting Emu Resonant Filters -- I don't remember this module too well but I remember it didn't seem to work in standard VCF ways but did a VERY interesting tuned percussion sound. Moe???
JB