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If modular is about anything, it's about modulation. The way we use voltage to keep everything moving and changing gives much of its unique musical flavor. It can transform a run-of-the-mill patch into something unpredictable, innovative and extraordinary. The simplest and most pleasing modulator we have is the LFO. There's something about the smooth ebb and flow of a slow-moving waveform that hooks into the natural rhythms of life.
There are many LFOs to choose from, but there's something about the øchd from Divkid and Instruo that keeps it up there as one of the most popular choices. Maybe it's the simplicity or the way those eight outputs find themselves patched in so effortlessly. Perhaps it's something about the relationship between them, and how, with a single turn of a knob, you can explode your rack into frenetic activity. Let's have a closer look.
The øchd is simple. It has eight triangle wave oscillators with useful bipolar LEDs, built into a nicely compact module. The oscillators are not synced but they have a relationship where they are tuned by ear to give a musically useful range of outputs. The speed ranges from fast at the top to slow at the bottom with a master tempo knob that scales all of them at once. The way it seems to work is that you grab an output and patch it into something that you want to set in motion. You then grab another to push some other control around. And very quickly, you've got half a dozen elements in motion all being controlled from the one device. They never feel out of sync; instead, there's an organic drift to it that just works in almost every patch.
If you have the time, you can wind the slowest LFO down to a 25-minute cycle. And if you add a bit of CV to the input it can go even slower than that. If you apply a negative voltage to the input, you can also stall the LFOs with a Track & Hold-like function.
At a basic level, you can just patch it into stuff and enjoy the movement, but here are a few pointers for interesting patches and experiments.
Simply Modulate
I think what's so great about the øchd is its ability to throw thoughtful modulation into any space. You're not having to worry about being precise or syncing things up as it all somehow manages to flow with itself. And you have lots of them from a very compact module. It's elegant, looks great with those soft LEDs visualizing the movement, and it's no surprise that it remains a useful module in so many cases.
Tracking and Holding
"Track & Hold" is very similar to the probably more widely known "Sample & Hold". With Sample & Hold, you grab a sample of an input signal and hold onto that value until the next pulse, when it samples the input again. With Track & Hold, the input is being followed and then holds a value when it receives a high gate. When the gate goes low, the input passes back through again. Under certain circumstances, they produce pretty much identical results, but in the case of the øchd what Track & Hold is doing is pausing or freezing the path of the modulation and then letting it flow again.
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The practical use is the ability to pause and restart modulation. So you could have an output of the øchd sweeping a filter cutoff that then pauses for the duration of a gate. It can interrupt a patch that has massive modulations going on and set it all static, or conversely, drop in a bunch of modulations at the release of a gate. If you have a way of creating gate patterns, you can feed those in to give a rhythmic character to the modulations.
Setting it up requires you to patch a gate into the CV input and turn the attenuverter all the way down to the left. When the gate is high, the øchd maintains a steady value at each of the outputs. You can spice things up a bit by using an envelope to shape the suddenness of the pause and release. Simply patch the output of an envelope into the CV input and apply the gate to the envelope.
Chord Fading
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The oddly pleasing relationship between øchd's LFOs is perfect for injecting a sense of wonder into the notes of a chord. Have a few notes droning from a handful of oscillators and patch them into individual VCAs. Then patch different outputs of the øchd into the CV inputs on the VCAs.
The result is this organic tumbling of notes as they fade in and out. At faster speeds, it picks up a sense of urgency and pulsing, whereas when you slow it down, it becomes the slow waving of tree branches or the drifting of boats on the waves.
I'm sure you can imagine how great this concept would sound if applied to filter cutoffs, or harmonic levels, EQ parameters, wavetable surfing, effects levels and so on.
Waveshaping
With a little bit of feedback patching, you can push the øchd into making some very unexpected shapes.
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For this, you patch one output into the CV input and turn up the attenuverter. Which output you use and how much positive attenuation you apply is very much down to experimentation. If the LFO is too slow it will simply modulate the speed of the other LFOs, which in of itself is very cool, but the interesting stuff happens with a faster output. The result also varies depending on the output. I find using a middle output as the feedback gives fascinating waveforms at the outputs on either side. Also, make sure you experiment with the attenuverter level, as there are many possibilities to explore.
Getting Complex
But that's not the end of the story: Divkid and Instruo cooked up an expander that adds unexpected levels of complexity and another 16 outputs.
The Expander has four sections of four outputs that have outcomes derived from the original øchd LFOs. The top section are full-wave rectifiers, pumping the outputs of LFOs 1, 3, 5 and 7 up into only positive voltage. The next section gives logic OR outputs based on a pair of LFOs. Section three generates triggers from the four even-numbered LFOs, and the final section uses 4-bit DACs to generate four versions of noise or random values.
It is, of course, slightly more complicated than that, and so here are some more details.
The Rectified outputs flip the negative part of the triangle wave up into the positive voltages, giving a unipolar output. The result is a doubling of the original frequency, giving a unique LFO rate.
The Logic section has two analog diode logic pairs that combine a pair of LFOs to give the highest (max) value and the lowest (min) value present. The max and min outputs offer reflections of each other as modulated triangular pathways. The left side uses LFOs 2 and 3, whereas the right side uses the slower LFOs 6 and 7.
The Trigger outputs are cascading triggers that start at the rising edge of the LFO. If left unpatched, each output will contain the triggers of the one that went before it. So the fourth output will contain triggers generated from LFOs 2, 4, 6, and 8 until you patch the other outputs to somewhere.
The 4-bit outputs have something to do with 4-bit Ladder DACs and use the most significant and least significant bits to effect a voltage change. The rate of each LFO pushes it into different flavors of what they call "slow noise"—but what we most commonly call random voltage.
When combined, you have endless ways you can change, mess with, and modulate your system all hanging together and depending on a single tempo knob.
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