Analog has a lot of detail that digital doesn't. Real circuits are imperfect in all kinds of interesting ways. It's not just randomness, it's specific kinds of

Analog has a lot of detail that digital doesn't. Real circuits are imperfect in all kinds of interesting ways. It's not just randomness, it's specific kinds of non-ideal operation - distortion, non-linearity, noise distributions, and other fine details. It's trivially easy to make idealised digital models of VCO-VCF-VCA but they sound sterile and boring. The more imperfections you model the richer and more interesting the sound get, but the more processing power you need. Good models - especially good models of analog filters - are incredibly difficult to design. And even the best aren't as smooth as the real thing, because - for example - with a filter you may have to recalculate a load of coefficients for every sample. A lot of digital models get in the ballpark now, but very few do better than that. And there's a fair amount of secrecy among DSP coders. There's no mystery about the basics, but the manufacturers like to keep the best models to themselves. So the big computer music tools - like Csound and Supercollider - have third or fourth rate models that are a good few generations behind the latest code. So it's still hard to get comparable sounds of pure digital synthesis. The new M1 chips are fast enough for better models, but you'd need about 5X to 50X the processing power - and more research - for no-compromise digital replacements of vintage analog hardware.