Yes, well spotted. It may of course be possible to do something similar with a range of synths, but the Synthex clearly does it, and it's a glaring omission in the available software synth emulations so it would make sense to do it.
Actually when Xavier first dropped a hint about the interesting filters I immediately checked out the specs for the Synthex to see if that would apply, so it looks like you and I have been thinking along similar lines. Did you happen to notice the Synthex similarity by pure chance, or had you been suspecting something to start with?
Of course we could be completely wrong and it's going to be a Doepfer modular or something, but I'm pleased to find someone else thinking along the same lines I've been on with this.
I'd REALLY like to see a Rhodes Chroma added. It would fit in well with the slightly oddball synths XILS has been creating and is absolutely gorgeous sounding. So please, for all that is sacred, make that next!