Which is, itself, an application of a Schroeder-Moorer reverberator design, developed, originally, by Jezar at Dreampoint for C++. Which also means it is a sort of “primitive” digital reverberator; these algorithms have a fairly distinct sound, which is more in line with a “tuned room” than a big ambient wash. (For this reason, I think they sound pretty good on percussive material, but they aren’t the go-to for washy, dreamy stuff.)
If you want to learn more about the design, I used this as a reference for the patch: https://www.dsprelated.com/freebooks/pasp/Freeverb.html
You might also check out meanmedianmoge’s pack of primitive reverberators, if you’re into the sound: https://patchstorage.com/schroeder-reverberators-three-takes-on-a-classic-reverb-design/
Anyhow, I took the basic Freeverb design and added some elaborations upon it (and made some compromises for DSP; the original design is in true stereo; here, the signal is summed to mono before a stereo image is created using the same methodology that the original Freeverb program uses, which applies the Haas effect to produce additional delay on one side of the algorithm; the dry signal is stereo). Essentially, I introduced some additional controls for the diffusers — Schroeder all-pass filters — used to generate the tail of the reverb, which allow to move beyond simple room sounds into reverbs that bloom a bit more.
It’s a pretty basic reverb in a lot of ways, but I agree with the assessment in the linked file that it is well-tuned, which is 90% of a good reverb; tuning delay lines is really tricky business.
As I mentioned already, the patch sums the wet signal to mono before creating a stereo image from that summed signal. The dry signal path is stereo throughout.
Left stompswitch — maxes the decay-damping control (this also exposes the loop points of the reverb quite a lot, so it’s not the best for creating “frozen verb” sounds, but it can be an interesting effect)
Across the top are the basic controls of the freeverb design:
Delay structure — at .5, the delay lines are tuned to the original freeverb sizes. I think these sound the best, but I figured I’d let you mess around with the delay lines, because why not. So as you set the delay structure control smaller, the delay lines also become smaller and more comb filter/resonant-like. At larger values, they have more of a slapback/echo sound.
Decay-damping — determines how long the sound persists; you will notice that as the decay is pushed, the artificiality of the reverberations becomes much more apparent
Room size — you might think of this, alternatively, as the absorbency of the room’s materials, since it controls the frequency of low-pass filters that follow the delay lines and are placed in the delay lines’ feedback loop
Across the middle are additional controls for the tail/diffusion:
Diffusion — this affects the gain and diffuser size simultaneously. At 0, the diffusers have the settings of the original freeverb. As you increase the diffusion amount, the tail of the diffusers will become… mushier? Bloomier? It’s sort of hard to characterize, but the sound definitely becomes more diffused!
Diffusion mod rate and mod depth — you can add modulation to the tails; the depth control is tied to the diffusion control, so it will only have affect when diffusion > 0.
Across the bottom are controls for the output/mixing:
Stereo spread — determines the length of the delay used for generating the stereo signal
Wet and dry signal — fairly self-explanatory; the wet signal can go somewhat above unity