OK I think I've worked out what ITER is

Been playing around with it the last few hours, and thought a description might help the people that keep asking.

From what I can tell, ITER is a basic sine/tri sounding tone (kind of Rhodes-y). What makes it interesting is a weird resonant filter/feedback/env circuit. Controls as far as I can tell are:

BLUE: Filter env. amount (like “contour” on a minimoog)
GREEN: Filter env. speed (min= quick, max= slow)
WHITE: Cutoff (only works with BLUE turned up
RED: Filter cutoff modulation amount (sounds noise-based to me)

So, with all dials at zero, you just get a basic sine/tri tone. Messing around with G, W, and R does almost nothing without turning up the BLUE control. Which is weird, and probably why it feels a little crappy when you first use it. But, with a combo of the amp env you can get some multi-stage env. shapes that are otherwise impossible on the OP1 as it only has the one envelope usually.

SO, in a way, ITER is kind of like a Volca Kick - a resonant filter with a filter cutoff env./modulation. It can make some MASSIVE kick sounds, and bass sounds in the low registers. In higher registers the RED control makes it pretty unstable/random/noisy sounding at high levels, but functions really well to give that weird organic vibe to the following notes as a rhodes-y kind of sound.

PROS: Good Rhodes sounds, really thicc bass sounds, weird organic vibe due to the noise-based modulation, psuedo-dual-envelope when combined with the amp envelope
CONS: bit weird that nothing does anything without the BLUE knob up, envelope is ONLY descending (can’t flip it), some SHIFT controls would have helped (e.g. shift+blue could control direction of envelope), feels random at times

Hope that helps! Def worth the download IMO

I love the iter synth!

One hopes that maybe a future firmware will hav a finished design and make this thing official.

I’m getting a different feel from it. Like some kind of feedback network? I’ve got ITER generating some nu-autechre style metallic percussive sweeps. Almost like what I had hoped to get out of the FM engine, and now reminding me of recent experiments I’ve done on the DSI Evolver with FM and heavy feedback with short delays.

But that sine wave is still at the heart too. Very strange little synth, this Iter.

I still haven’t tried it, and now I forget how to get it…

@ludicrouSpeed AFAIK you just need to import and load a user patch that uses ITER (there’s one for ITER and FILTER linked here in the forum somewhere). The synth is implemented, but simply excluded from the listing.

Thanks @millbastard, really appreciate the insight. It’s great when we are fast tracked by people with the knowledge on op-1 synth engines.
@ludicrouSpeed try this link. It’s from @wavi.

ive found that iter doesnt respond to any of the sequencers, which is a shame cause its a cool engine. wish te would flesh it out more

Iter does work with the internal sequencers for me

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