LPD is basically a standard buchla-style LPG, followed by a gentle waveshaper. The effect is of a little extra grit, and harmonics, particularly as the LPG is fully opened. I’m sure any distortion module would get you most of the way there, provided it can be subtle enough.
Indeed the circuit for the isms Follow is near identical to the Follow out of Cold Mac. It’s a slightly modified ARP2600 envelope follower, though there’s probably more sophisticated EFs on the euro market.
