[sdiy] some buchla LPG questions

[matt holland]

A friend of mine is in the process of trying to make a digital
emulation of the LPG and asked me to help him out by coming up with a
transfer function for him (with the filter in low pass only mode).
i've been looking at this easier to read version by peter grenader:
http://electro-music.com/forum/phpbb-files/buchla_292_clone_191.gif

It would be great if I could ignore the 4.7M resistor and 220pf cap so
I could map it to a standard sallen-key filter and avoid pages of
tedious algebra, but i wanted to get some opinions on that first.
so...

what exactly are those components doing?
are they vital to the character of the filter?

less important questions:
-the initial 1uF cap is probably dc blocking, but what are the 100k
resistors doing? my only guess is that they provide a discharge path
for the cap regardless of whether it's holding a positive or negative
voltage?

-what is the significance of the 1k output resistor? i'm guessing it
will form a 100k/(100k+1k) voltage divider like the signal in, but
why?

any insight greatly appreciated,
mh