I grabbed a few of these from musicians friend when they were blowing them out at $10 a piece…
http://www.musiciansfriend.com/product/Rogue-VP201-Stereo-Volume-Pedal?sku=150050
in hopes that I could mod it to use with my newly acquired mf-104z…looking for any info or links on how to make it usable. 
you’ll just need a voltage source. this can be from your synth or mooger (cv out, lfo out, S+H, et.). patch it to the pedal input, and then patch the output to your destination. This patch will allow you to use your volume pedal as anattentuator for the CV signal.
Or you can hook up a 9V battery to the pedals’ input (I think positive to the main lug, negative to the ground lug) and you have a variable 0-9V voltage source. This is useful for filter sweeps, etc
The expression pedals are completely passive, no voltage source needed. All you need to do is this:
The only thing you need from the exp. pedal is the potentiometer, disregard all other circuitry in there. If the 1/4 inch jacks in the pedal are not TRS (they probably aren’t) you will need to swap them out with ones that are. There will be three terminals on the potentiometer, connect one terminal on the pot to one terminal on the TRS jack. I don’t know which terminal goes to which, but just keep trying until you get it right. This might take some trial and error. You won’t hurt it if you hook it up backward, the control will just sweep in the oppoisite direction.
thanks oysterrock!
alternate question:
which non moog expression pedals work well with the moogers? I’ve been told the yamaha fc-7 and the roland ev-5…but I’ve also heard bad things about ev-5s…
What bad things have you heard? I use one all the time and haven’t noticed any problems. Is it an issue of construction or perhaps the range of the pedal?
perhaps range? no one has given me a very thorough answer yet.
I’m using a cheap M-audio pedal and it works great. I was a bit apprehensive after having purchased a cheap expression pedal long ago that had ok travel, but swept the entire value of the potentiometer within the middle inch of travel, leaving the rest of the physical travel useless (or worse, nebulous and confusing). The M-audio pedal works fine, though, and I’m planning on buying a few more. I’ve heard the Moog pedals have a very long travel, which could be a bit more expressive, but they are pretty expensive. Maybe try a few different pedals in a music shop first before you buy one.
I forgot to mention that one thing to consider is that the pot from a volume pedal is probably logarithmically scaled. Expression pedals use linearly scaled pots, so you may need to swap the pot out altogether for a linearly scaled one. Just make sure it fits and that the the little toothed gear from the original pot will fit on it.
I ended up getting a yamaha fc-7 and it works nicely…has a long sweep.