We use JUCE for building the app/plugin. It handles the GUI, the audio/MIDI devices and the plugin API. The synth engine was originally developed to run on a STM32F4 (what the Anyma Phi uses), so almost everything is purpose-built (with good old Makefiles). On the hardware, we use an immediate-mode UI and it's hard to go back to something like JUCE, which is flexible but a bit quirky. I often write GUIs with Cocoa for our internal tools (simulators, DSP models, etc) during the development of our hardware products and it's a much more comfortable environment.

In 2019 I had an early version of the Anyma engine running on Dear Imgui, it was really fun, but it would have required too much effort to properly manage audio/MIDI/plugin aspects in a cross-platform way, and the backends were incomplete at the time. JUCE was too much of a time saver to ignore for a team of 1.5.

I'm curious, if you don't use C++ and JUCE, what is your stack?

Did you entertain choosing anything outside of juice?

We also investigated iPlug2, but ultimately decided on JUCE partly because it was easier to find help.