I want to achieve the sound of drifting pitch on the dfam.. say.. how a cs80 has a sound of vintage and nostalgia as the oscillator seem a little unstable.
-- Dfisound
Huh? That's not the key to the CS-80 sound, unless you want it to sound utterly hammered and miscalibrated. Mine sure doesn't sound like that...unless I'd kicked it down the studio stairs (and risking broken bones from that kick...remember: this mofo weighs 225 pounds!).
You're probably confusing that with what you can do with modulation via the control "tabs". That can get really elaborate, too; Yamaha didn't screw around when they cooked this thing up. But the "CS-80 sound" really has more to do with the architecture of the voice path, the ability to get at piles of functions rapidly with those tabs, and those FILTERS. And I'm not even going in depth on the ring-mod circuit, the ribbon controller, and so on...plus, the "preset" hatch makes a good place to keep a sammich handy for snacking while playing (DON'T ACTUALLY DO THAT! Seriously!).
Another possibility to go along with Jonau's suggestion above would be to check some of Nonlinearcircuits' slow chaos modulators. Since these can do random voltage movement at EXTREMELY slow rates (like, days at max), you can simulate VCO drift with these very easily.