Softube Modular is a modular analog synth emulation, presented in a rack format. You are given a range of modules, a rack to put them in, and endless virtual cable. Each module may be instantiated as many times as your computer can handle, and it is designed to be very close to a 1:1 emulation of its real-world counterpart.

Modular ($89) comes with a bunch of Doepfer modules, plucked straight from real life and digitized for your virtual pleasure. These include the Doepfer A-110 VCO, a typical analog oscillator with sine, triangle, pulse and sawtooth outputs, CV-controllable frequency and pulse width modulation, and a sync input which will reset the phase of the oscillators when fed an impulse or zero-crossing.

Doepfer’s emulated filter is the A-108 VCF8 – a mostly low-pass filter with output slopes ranging from 6 to 48 db per octave and a band-pass output, all of which, like the oscillator outputs in the previous module, can be tapped simultaneously.

Also included from the real world are a dual VCA, a typical ADSR envelope generator, an LFO, and a noise and chaos generator. On top of these are a bunch of utility modules: a pure sine-wave generator (which is mathematically perfect, unlike its analog and virtual analog counterpart), sample and hold, mixing and logic modules, pulse dividers, sequencers, and splitters and combiners.

Do It Yourself

Modular does not hold your hand. Here’s your rack, here are your modules, get wiring! Luckily, the product comes with quite a few tutorial patches and a short but to-the-point manual to explain how to make connections and the function of each module, as well as an explanation of each and every output and input.

Even so, I am glad to have cut my teeth on modular synths such as U-He’s ACE and some very simple semi-modular analog gear of my own, because modular synthesis is the sort of field where experience is as vital as knowledge. Mastering an all-in-one modular or semi-modular synth beforehand is recommended, but not essential, to tackling Modular. With my mentioned previous experience, I was able to wire up a sound fairly quickly with Modular, from about ten minutes after starting it up.

See also: Softube Heartbeat Review

The GUI is highly literal. Only the connection cables look unlike their real-world counterparts, being coloured lines which all show up with a degree of transparency when you mouse over an input or output, with any connections made to or from the jack under the mouse being solid to allow you to trace the signal back and see where it is flowing from.

Things can get cluttered and confusing, especially when two cords with the same colour are flowing in parallel and in close proximity, but that tends to be the nature of the beast. This is a real-world problem as well, and can’t really be avoided, although I think I prefer the parabolas of “virtual patch cords” than I do straight lines, simply because with variable tension there is less chance of overlapping and obscuration.

Multiple outputs from each module may be routed from an output jack to various inputs, but there doesn’t seem to be a way to move groups of them around. You can pick up a wire going into an input and move it to another input, but you can’t do this for outputs. Suppose I have a square wave output on an LFO feeding two inputs on different modules, there seems to be no way to grab them from the LFOs end and plug them into the LFO’s sawtooth output, for example. There may be a good reason for this, but I’ve done it in other modular virtual synths, so it seems like something that should be possible.

Connections are deleted by grabbing the “to” end of the cable connected to some input jack, and attempting to connect it to nothing, at which point it disappears. CTRL, ALT, right mouse button and SHIFT-clicking could all be put to use to make things a bit easier, but on the plus side, upon grabbing a virtual cable, all the places it can go will light up, which can help to clear up some of the confusion that may accompany exploring the world of modular synthesis.

Hear It Yourself (Yes, that’s a command!)

So, the GUI isn’t the most user-friendly thing on the planet, but it follows the real-world process of building a modular synth. This one-to-one emulation is also the big draw when it comes to sound. Softube claim they have modeled each component of each module accurately, and I believe them.

See, getting a good analog sound isn’t just about removing digital artifacts such as aliasing and clipping. Most analog units have their own set of quirks and artifacts in the way they respond to everything from pitch tracking to FM, right down to how the waveforms are created and manipulated.

The Doepfer modules emulated inside Modular are very popular in the world of modular synthesis, and while I have never used one myself, I have heard and watched enough of them online to be able to do a reasonable comparison. They are spitting images of the real thing. Since I’m not qualified to go beyond that with regards to comparisons, I will say, I absolutely love how analog these modules sound, from the weird little notch in the triangle wave, to the way the filters and oscillators respond to FM, to the way sounds vary across the keyboard.

In addition to these absolutely gorgeous essentials, a number of utility modules exist to tie everything together. My favourites from the bunch are probably Signal Tool and Logic Tool. These let you take two signals and combine them in various ways to make a new one. You can mix different filter outputs to create new filter responses – for example, mixing a low-pass filter with a phase-inverted clean signal gives you the equivalent high-pass response. You can combine waveform outputs in various polarities and volumes to create new wave-shapes. Combining waves from different oscillators at different frequencies inside Logic Tool will let you do things such as logic synthesis (for a very digital sound without horrible aliasing), or output a hybrid wave which only ever outputs the lowest value of the two oscillators, which is similar to amplitude modulation.

This kind of synthesis always holds its own in Modular. You can create digital XOR-type ring modulation waves from two different frequencies that track the keyboard, play them at a high pitch with vibrato, and hear no digital artifacts. Throwing in oscillator sync and FM, maybe a bit of feedback, and still, you will only hear analog-style sound. You can use modules however you want; for example, by using the VCA to modulate the volume of one oscillator with another, just by plugging one of them into the CV input. Feedback loops of cause-and-effect quickly lead to very interesting sound experiments which would typically end up sounding horrible in the digital domain, but sound rich and vivid in Modular.

I have tried all of this and overall am having an absolute blast and enjoying the sound. I really can’t fault it in any way – it’s like owning a modular system. The only thing I was missing was a simple way to remove DC offset from a signal and a simple ring modulator. Although both of these are possible to build out of what is already present, a simple DC cut module would be convenient, and, as many analog ring modulators have their own tone and unique response, some kind of branded emulation would be a perfect future treat.

Crossing The Rubicon

And now, onto the real reason I’m here. Yes, the Doepfer modules are fantastic emulations and make the perfect base to build off of, but the Intellijel modules: Rubicon (oscillator), µFold II (wavefolder) and Korgasmatron II (dual filter) really send things off the map!

Rubicon is, like its real-world counterpart, something a bit special – a triangle-core oscillator with hard sync, reversing soft sync, several frequency modulation modes (including through-zero FM) and stacks of simultaneous waveform outputs (including waves that oscillate at half and double the input frequency).

Softube Modular with Intelijel modules.

Softube Modular with Intelijel modules.

Why this is all exciting to me would actually take up an article on its own to explain, but I can summarize it by saying that it’s a complex oscillator with a lot of character. Performing synthesis operations on it is quite different from doing the same thing on a perfect, artefact-free digital synth or an emulation of a typical analog oscillator. With two of these oscillators linked up and influencing each other at audio rates, complex Buchla-like tones come pouring out of the virtual jacks, reminding me of Doctor Who and early electronic experiments from before the days when synthesis became routine with a well-trodden path.

Some of the neat touches in Rubicon are down to the way that sync works – sync triggers are created whenever the hard edge (or transient) of a saw or pulse wave enters the sync input, so not only does the master oscillator’s pitch affect the synched wave’s timbre, but its shape does, too. Using a modulated PWM wave as the sync master will create asymmetric triggering, chopping up and moving around parts of the slave waveform. Soft or “flip” sync doesn’t reset the slave waveform at all but instantly reverses it, eschewing the hard edges of typical sync sounds in favour of something more soft and slippery. The flip sync input jack also has an attenuator, allowing you to decrease the probability that a sync trigger will be created, which can lead to all sorts of weirdness such as sub-harmonics and peculiar jumps in the perceived pitch.

Likewise, PWM is offered in two main flavours, the typical one we are used to, and a symmetrical variant, where both the rising and falling edge of the pulse wave move towards or away from each other. In normal functionality these sound identical, but the latter can sound a lot more stable pitch-wise when fast to audio-rate frequencies are being used to drive the PWM.

Rubicon is amazing for creating organic, constantly shifting timbres and can easily move into the territory of chaotic drones, sound effects and experimental noise, all the while holding its own when high notes are played.

µFold II is a wavefolder, a type of distortion effect which causes the “clipped” portion of a signal to be mirrored back inwards, only to run the risk of bouncing again (and again, and again) depending on how many fold stages are switched in (from 2 to 6). This is a kind of wave-shaping synthesis which has typically sounded horrible on computers, even with oversampling, so analog emulation is the only way to go. It tends to sound best on dark signals such as the triangle, sine or heavily filtered waves, as it tends to make timbres more complex and bright, often sounding like FM. Louder signals will receive more folds, so an amplitude envelope beforehand is a great way to create punchy sounds whose spectra decay from bright to mellow without a filter in sight.

Another important control is Symmetry, which adds a constant DC offset to the signal before it’s folded, which has the effect of moving parts of the wave around as they hit different parts of the complex distortion curve. This can create sounds similar to PWM even with a sine wave, but the field is wide open for exploration as this is one of the less-explored areas of synthesis.

Finally, we come to the Korgasmatron II dual multi-mode filter. To be honest I hate reviewing filters, because trying to explain why a filter sounds good is tricky without resorting to hackneyed phrases. Rest assured, I absolutely love the sound, the unique resonance distortion control, and just how unusual and refreshing it is. It handles unlike anything I’ve used before, but you can hear it in action at several points in my audio demo above.

Sendy's custom Softube Modular patch which you can hear in action below.

Sendy’s custom Softube Modular patch which you can hear in action below.

For a more concise demo, here’s a short recording of this patch I made (pictured above), with various knob tweaking to show how many different organic textures can come and go.

Things I Haven’t Yet Mentioned

Finally, some caveats and things I forgot to mention: It’s a CPU beast, though not as mean as I was expecting on my computer. Polyphony can be either mono, or four-note, but when making a four-note polyphony patch, bear in mind you’ll probably need four of everything – just like in real life!

Velocity and other midi signals can be used as CV sources, and you can install banks of sliders into your rack which can move any combination of knobs or controls in any amount – so unlike in real life, you have a virtually unlimited army of hands willing to turn knobs for you, allowing for massive morphing potential.


I’m in love. If you’ve ever watched someone messing around with complex analog synthesis on YouTube and just drooled, or if the thought of a wavefolder in a feedback modulation loop makes you want to sell your house, this right here is the next best thing. Just make sure your computer and workflow can handle it!

More info: Softube Modular ($89)
Sendy On Bandcamp: click here
Sendy On SoundCloud: click here

Softube Modular Review


Sendy is in love with Modular. Enough said.

  • Features
  • Workflow
  • Performance
  • Design
  • Sound
  • Pricing
Share this article. ♥️

About Author

Sendy has been making music in her bedroom since she was 14 using computers, synthesizers, samplers, and whatever else was at hand. She does not subscribe to any one genre but enjoys energetic, constantly changing rhythms, disorienting synthesizer manipulations, and heroic chiptune melodics.

Leave A Reply