Google translate is your friend
http://translate.google.com/translate?j ... ge%3Dtb303It is filter FM (with level) which he is tweaking and the external input as I suspected. When you run an external sound source through the ENV and VCF, it is pretty hard not to sound like a 303 but I have had some very cool results with metallic and bell sounds from my TX (I assume you saw my video) I did the FM mod for a customer recently and the results were meh. Maybe he tweaked on the mod some but from my experience, the VCO is too fast as a mod source so there is a tiny little sweet spot that sounds good, and the rest is crapfest. A dedicated LFO source (external) would be better IMHO