Casio CZ/ VZ/ FZ - Pro Series

Hello,

I have been an owner of a CZ-1 for years. I recently bought a CASIO HT-
3000 and to my surprise found that its 'SD synthesis' engine was in fact 
a scaled-down PD synthesis with one analog VCF added.

I believe that its so-called DCO is actually a set of two PD oscillators 
with ring mod and maybe noise mod. They don't seem to have resonant waves 
or 8 step env like CZ, so I said 'a scaled-down PD synthesis.'

There are few resources on the net about its synthesis engine, and my 
speculation is almost based only on my ear and years spent with my CZ.

This could have been my dream machine - if only I could edit the PD oscillator 
section!

If you know something about SD synthesizers (HZ and HT), especially how 
to deeply edit its sound and its relation to PD synthesis, please tell 
me.
Sorry if this is off-topic, and sorry for my bad English as I am a Japanese..
. Thanks.

Best wishes,
Sealed