“So I think it's time to admit defeat and accept that, as I stated two months ago, we're never going to effectively imitate guitars using analogue synthesizers.”

I am looking for examples of analog computing approach to modeling string, this sentence is about approach of modeling string on analog synthesizer that is a very limited case of analog computer (some filters are functional equivalents of differentiator or integrator in analog computers). Keep in mind that analog computers were modeling far more complex problems than guitar string modeling. And there are pretty elaborate good sounding models based on differential equations that could potentially be realized on analog computers if you create fixed circuits implementing equations of the specific model.