I’ve had my er-301 for a year or so now, and I have to say its the kind of module that keeps jumping around for me. I want it to do everything it could possibly do, all at once.
I thought I would ask, how do you use yours?
is it the whole rig? or part of a larger network?
And if that, then what roll does it end up playing for you?
I have two in a small case with a mixer and some fader CV controllers. They do everything with the help of a Cirklon sequencing and a TB-303 that’s also being processed by one of the ER-301s. They make up 90% of the sound generation in my setup.
I use mine primarily for mixing and effects, taking an external sound source and sending to effect chains. I also use it for playing one shot samples and as a wavetable synth. Using it as a mixer is useful because it has so many potential audio inputs. I generally use channel 3 and 4 as left and right output straight to a headphone jack. Channel 1 and 2 can be effects sends, a mono voice, audio rate modulation, etc. I generally mix an external mono voice, an internal mono voice, a stereo drum machine, and up to two stereo effect returns.
Soon I’m getting a 16n which should make controlling it all even easier.
The 301 is the IDM drummer of my dreams. And ditto on the 301 as a mixer, it excels at bringing everything together. I also use it as an automated looper pretty often, Mission of Burma style, to chaotically reinsert old material into an ongoing performance. I would love to put it in a rock context with some friends but, covid…
In the last 6 months I’ve been building up a 7U case with it more or less as the end of chain. Before that I used it in a 3U 84hp skiff. Sometimes I miss being able to focus on the 301 really intensely and make it do almost everything. Doing so much on it made for easily recallable patches, too. In a larger system my attention feels a lot more spread out, of course. I definitely plan on having a micro satellite system in the future just to get that focused feeling back when I want to.
Something I used to do more often in my small system was to use the 301 as a matrix mixer in feedback patches with 3 sisters. It’s lots of fun making complex networks of FM between the two.
I use it mainly for sample manipulation and playback, but sometimes also just as a flanger, you know, whatever I need from it. I have a pretty large system, and find myself pretty much always using it in one context or another. I don’t dive that deep into it anymore though, I kind of suck at finding useful patches to build with it. Thankfully there’s a lot of cool folks in here sharing their patches, and they’re a lot of fun to use and alter to your needs.
I really look forward to the upcoming “share a patch” feature, I hope i can clean up some of the mess on my 301 with it.
Mine’s in a mid-sized 16U system. It’s always my end of chain mixer and often the recorder. So it gets used in every single patch.
Beyond that my usage varies wildly. It’s my super-flexible Eurorack-integrated DSP playground.
Over the years I’ve had it, I’ve learned to not have it do everything it possibly can all the time. Not that there’s anything wrong with that. But of course you will eventually hit the CPU wall with that approach and might start feeling guilty about neglecting your other modules. 
I do think it’s a great way to learn it. I definitely focused intently on it for a long time and still periodically engage in deep 301 study. And I think doing that has helped inform in what contexts I want to use it vs another module for whatever task.
That’s probably more vague than you were looking for. But it really varies a lot. One day it might be that the 301 is the only module I have that can grain stretch a sample’s length independently of pitch and stitch it back together seamlessly. Another day it might be that I think the character of the 301’s LPF is really the one I need to bring a particular sound to life.
I really tried to use it in a small case with some CV controls modulation, I found I learned the UI well enough in that situation, but it didn’t match my way of making music, because it was separated out from the rest of my gear. In the end, I put it in my primary 7U case, and use it way more often to fill in the blanks (oh, need a noise generator, add loopers, one shots, etc.). Love it in the context of other modules.
I use it both in a large case (16u) and a small case (Palette).
In the big case I use it quite simply, it’s processing some drums sounds, playing some drum samples as well, stuff I don’t have dedicated modules for. I never dig very deep in this situation but still, the little it does is invaluable.
In a Palette it’s much different since it does pretty much everything. I try to have one voice alongside it and some external sequencing/modulation (steppy 1u and pam). I don’t like creating sounds inside the 301; you’d need a ton of knobs/faders to make it work nicely, and I usually take the opportunity to dig deeper into both the 301 and the soundsource I’ve chosen. The 301 then does looping, sample playing, mixing and FX. It’s amazing. I usually hit close to the CPU limit when a track is done, but I have yet to try the 0.5 release.