The Fundamental plugin pack gives you a basic foundation to create simple synthesizers, route and analyze signals, complement other more complicated modules, and build some not-so-simple patches using brute force (lots of modules). They are also a great reference for creating your own plugins in C++.
Follow the build instructions for VCV Rack.
All source code is copyright © 2019 Andrew Belt and licensed under the BSD-3-Clause License.
The VCV logo and icon are copyright © 2017 Andrew Belt and may not be used in derivative works.