Assuming it might be an AU issue I tried the VST3 version and it mutes properly with the on/off button. That should be great, but clicking the show editor box opens once but didn't render the GUI correctly. I closed it and then upon attempting to reopen the editor the window WILL NOT relaunch in Axiom. This problem is repeatable.
Next, I tried the VST and it seems to work as expected though a similar GUI problem occurred when showing the editor for the first time. After that it renders correctly.
But when I tried to go back to the AU, to see if it had perhaps corrected itself, the editor GUI had turned into a giant blue monstrosity with at least 355 Axiom-style dials on it (my screen isn't big enough to see all the parameters). I definitely didn't sign up for that. It's also unusable since it doesn't even pass audio at all now!
I guess VST2 is the way to go but I've been thinking it would be nice to perhaps just use Audio Units or VST3 plugins since more and more software developers seem to be phasing VST2 out. It just seems very weird that the AU and VST3 versions display these behaviors when used in Axiom (not fully tested with PatchWork but when I tried to load the PatchWork Synth AU and host OS2.5 inside it, it rendered the giant blue dial screen too).
If you have any ideas on possible solutions, please share
