I don’t often hear mention of the Erica Synths Swamp module, but it’s one of my favorites. It’s a DIY random CV/audio generator, and it’s pretty special. In a way, it’s kind of like a Wogglebug, or the Turing Machine, in that it outputs a random stream of CV, but it doesn’t really have locking or repeating. It’s hard to describe, but there’s two oscillators that interact with each other, which generate audio as well, plus an input which does ring modulation with the generated audio. So there’s three CV outs, and three audio outs that all have different character. The rate of change, range of variation, and clustering of randomness can all be controlled with dedicated knobs. And then it can all be clocked, so the changes are in time, with clock division controlled by the big knob. You can even CV that as well.
It took a while to wrap my head around it, but I find that I use this module constantly, sometimes to add a bit of subtle variation to patches, other times to inject changing audio to a percussive low-pass gate or to mix with another effect. Unlike other random sources, it has a bit of wild character that takes on a life of it’s own. And as a DIY kit with excellent instructions, it was fairly easy to build. I highly recommend it, and it’s definitely that “one little module” for my taste.