atanh2()

[DJ Saint-Hubert]

I made a FuncShaper preset that does atanh but with two arguments, which in this case is the original signal driven two different amounts. Variables a and b drive it, c changes exponent/root, and d is another exponent to shape it more/less. Included is atanh2 diff.xml which does the same thing but returns the amount of expansion which you can route to a sidechain/use with parameter modulation and it works like an instant expander. You can oversample it too

[DJ Saint-Hubert]

not necessarily a mathematically perfect implementation but it works as I intended, as an instantaneous expander that doesn't click or anything