There are various projects around in which diodes are put in series with resistors, either alone or groups of them to achieve softer clip, plus asymmetric clipp

There are various projects around in which diodes are put in series with resistors, either alone or groups of them to achieve softer clip, plus asymmetric clipping when different number/nature of diodes are used; experimentation can lead to very interesting results. At one time I simulated using tunnel diodes too, which according to the simulation should have produced some unique waveforms due to their negative resistance, but when built my prototype didn't work at all. I had no experience with them however, so I may retry one day.