a most simple modular example is given in the pic above.
You can beef this up by i.e. using a pitch2cv module to modulate the cutoff freq by its output. This way the cutoff freq is always the same as the one fromn your signal. Or use a MCV instead and control the pitch by your keyboard. Or use a sequence module to make a gater fx.
Possibilites are endless and depend on the purpose, that's why I'm struggling a little bit to give some general examples

But there are some nice ressources for the nord modular, which are easy transferable to our beloved modular. I'm shure these explanations will help you a lot already.
http://www.cim.mcgill.ca/~clark/nordmod ... k_toc.html
http://www.clavia.se/nordmodular/Modularzone/
The project routing is quite simple as most if not all routing happens inside the mixer.
I'll post some setup as soon as I find time. In the meantime watch my video, there'a basic setup shown.
thanks,
Wolfgang