Hello HN, I'm the current lead maintainer of the ZynAddSubFX project. Some of you may have heard of the project in the past, though if you haven't been tracking it recently there have been a few major changes.

First and foremost the old fltk based GUI has been completely rewritten from scratch using a new custom toolkit (mruby-zest). This was done in order to make the interface more usable by making it easier to navigate, easier to use within plugin hosts, easier to get feedback, and easier on the eyes (the fltk UI wasn't exactly the prettiest).

Secondly the work on the GUI was made possible by some work which decopuled the sound synthesis engine from the interface. As of the 2.5.x series all parameters can be accessed out-of-process (or on a different networked computer) via open sound control. This decoupling has improved low latency processing and made it easy to map physical (midi) knobs/sliders onto the virtual ones.

Overall this work has resulted in a number of child-projects including the RtOSC OSC implementation ( https://github.com/fundamental/rtosc ), the mruby-zest GUI toolkit ( https://github.com/mruby-zest ), and the Stoat LLVM static analysis tool ( https://github.com/fundamental/stoat ).

I'm currently hoping that the large interface upgrade (which was supported with some recent crowdfunding efforts) will get more people interested in the project and help speed up the momentum of the project as a whole.