Supposing I wanted a custom EQ Effect for the audio busses that specifies the 24 critical bands used in psychoacoustics (https://en.wikipedia.org/wiki/Bark_scale). I don't suppose I could do this using GDScript. Would it be possible to do in GDNative? I'm comfortable with C++.
Edit: Oddly, it looks like there's already code for a 31 band EQ, which would also meet my needs: https://github.com/godotengine/godot/blob/master/servers/audio/effects/eq.cpp I wonder why it's not implemented?
Your best bet is to likely ask these questions in a new issue on the github repo.
It was likely deemed too specific. Feel free to open a pull request against the master branch to expose it :)
master