> germanium diodes generally have a softer turn-on than silicon diodes

This a million times, and it also applies to germanium transistors too. I keep reading that all it needs to emulate the germanium sound in a guitar fuzz made with silicon transistors is adding a small cap between base and collector, which is only part of the story: those are non linear devices, and there's a non trivial difference between Ge and Si V/I curves, which translate into different sound which can't be emulated just by adding a cap. A softer curve creates a much gentler distortion which doesn't ruin the sound when playing chords for example.

Another famous guitar effect example is the germanium "fuzz face" pedal, which are still in production today.

You can get an idea of this kind of fuzz sound in the song "Spirit in the Sky" by Norman Greenbaum.