While I've seen NANO modules around for a while, this is my first hands-on experience with any of the Barcelona-based company's modules. Quart, their quad-channel dual-function module with four independently cycling LFOs or four independent AD envelopes, has an elegant black+gold+white faceplate and an overall no-nonsense design with clearly legible text and well-spaced layout. Each of the four channels are identical with a RISE control, a FALL control, and a three-position toggle in between, highlighted with a white LED that indicates LFO or envelope level. At the bottom of the module are four trigger inputs—labeled T1-T4—and outputs for each channel below that. When nothing is patched into the trigger inputs, each channel is in LFO mode, outputting a unipolar 1-9V signal, with the RISE and FALL controls shaping the LFO and the toggle determining the speed of each; with slow, medium and fast time ranges for each with circles under the toggle to signify the speed, with the small circle indicating fast [RISE from 0.1 ms to 400 ms and FAST from 0.1 ms - 600 ms], a large circle indicating slow [RISE from 10 ms to 40 s and FAST from 10 ms - 50 s] and a medium-sized circle indicating, naturally, a medium speed [RISE from 2 ms to 4 ms and FAST from 2 ms - 10 ms]. I do find the circle positioning under the toggle a bit strange in that it goes [from L to R] SLOW, FAST, MEDIUM as opposed to a more expected [S,M,F or F,M,S] progression, but that aside, nothing about Quart is hard to grasp, and what you see is what you get.
In the fast mode, the LFO is in audio rate and while it doesn’t track at 1V/oct, you can use it to FM another sound source, tweak a filter cutoff, VCA, etc. I paired it with my Zlob Modular Vnicursal six-channel VCA and tweaking the RISE and FALL knobs in fast mode going into the CV in on the Vnicursal with random audio rate signals going through, and I got some cool ring modulation type sounds.
Since the LFO output for each channel is unipolar, it doesn’t behave the same as a bi-polar LFO. For example, since the lowest voltage the LFO outputs is a +1V, if patched into a VCA, the VCA never fully closes as it never reaches 0V [or in the negative voltage realm], so there’s always a little audio bleed at its lowest position. Is this a big deal? Probably not, just something to note, and in faster settings this idiosyncracy wasn’t noticeable at all in any of my patches.
As mentioned, patching a trigger into any channel turns each from an LFO into an exponential AD envelope generator, which outputs a 0-9V unipolar signal. This makes Quart a pretty cool, functional module as you can have any combination of AD envelopes and LFOs with which to modulate, and Quart pairs really well with underLFO/env’d synth voices that usually only have one LFO and maybe two envelopes. Unfortunately, there's no way to clock the LFOs to sync to anything, but I always like having random LFOs moving stuff around in my patches to give some organic human-type movement to things, and for this Quart worked well.
And while there’s no way to sync the LFOs in Quart, there’s also no way to CV anything at all, like the RISE or FALL, which could be considered a shame, but that just means that if you want to add more variation/change, you’ll have to actually turn knobs with your actual hands. The horror! This is something that should be done because Quart is really fun to play with, whether it’s being modulated or the one doing the modulation. Most of the time that I spent twisting and tweaking was when the toggle was switched to fast mode, though the medium speed worked fine for the most part as well, and I got a lot of cool FM/ring mod/tremolo things happening in various patch formations.
I’ve actually been hankering for a four-channel envelope generator for a while, so having the option for LFO modes was a definite bonus and Quart has been a very welcomed addition.

10 HP +12v 25mA −12v 6mA
Price: $220

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