Hi again Paul. The filter is primarily for Guitar players, I think because a synth player would have to place it after the VCA in the signal path,which is less useful but the others , although they can be used by guitar palyers to great effect, can be looked on as modules that will interface with your cv equipped synths. In the old days of modular synthesizers, people ofter ordered them module by module and these are just a descendant. They have a lot of ins and outs so you can feed a control voltaage source from your moogerfooger to a cv in on your synth or feed an external cv source into your moogerfooger so that certain of its parameters can be modulated. They are great things if you take the time to study their possible uses. I thnik the manuals are available on line from Moog, and the analog delay one (even though that module is no longer available) does a great job of explaining this.