This is an FDN reverb based on a design by Manfred R. Schroeder in his 1962 paper, Natural Sounding Artifical Reverberation.
The algorithm consists of a 6 delay lines in series, feeding into 15 series allpass delays each, with allpass feedforward/feedback around every delay line.
To build using CMake, run the following in the repo directory:
$ cmake -S ./Source -B build
$ cmake --build build
You can download CMake from here