Review – Synth Modular by KarmaFX

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Synth Modular is a modular synth, exactly as its name suggests.  Our reviewer finds much to like about this versatile and highly flexible instrument.


by Rob Mitchell, Sept. 2014


KarmaFX is an audio software company based in Denmark, and they’ve been around since 1998. The first release of their synth called Synth Modular was back in 2007, and since then it has received great reviews, and even picked up a Computer Music Value Award.

Synth Modular is just like what the name suggests; a modular synthesizer plugin.  Instead of being stuck with a certain configuration, a modular synth uses many different modules you can connect together in nearly unlimited ways. Each module can either create an audio signal, or change/process the audio.

The system requirements for Synth Modular are pretty low by today’s standards:  If you have a PC, you’ll need a 2 GHz Pentium-based computer with XP, Vista, or Windows 7 installed as the operating system. It doesn’t mention anything about Windows 8 in the manual. For the Mac, the manual mentions it must be Intel-based, and OSX 10.5 or later.  There are 32-bit and 64-bit versions of Synth Modular for the PC and Mac.

After you’ve ordered it from their website, the version you download has your information burned into it already.  That way, it has its own built-in copy-protection, instead of using a serial number or some other more intrusive method to get it working. Just download, install, and that’s it!

There is no standalone version of Synth Modular, but there is an FX version you can load on to your tracks. I wish every synth plugin had this feature. You will need some type of host to load it into, and for my review I used Cakewalk’s SONAR X3 Producer.

The manual is very good, and explains everything in detail. It also goes over a lot of terminology having to do with synthesis in general.  It’s a great read, and is very informative.  This can really help people starting out when they’re programming their own presets, as they can understand the real meaning behind all the terms. They might be thinking: What is a filter? How does modulation work? What is additive synthesis? Reading through the manual will cover nearly anything you’d need to know to get started, and has some advanced topics as well. 


The Modules

Synth Modular has many different types of modules that are divided up in to certain categories, and they include Generator, Amplifier, Filter, Effect, Modulator, Controller, and Output. The Generator types you can choose from are Osc1, Osc2, Sampler, Additive, Pad, Noise, and Input. I will get into more detail on these Generator types a bit later.

To add a module on to the workspace, right-click the screen and select “Add Module” from the menu that appears. You can also get to the manual from that same popup menu.

There are four buttons on the right side of the module’s waveform display. The first button turns the display on or off (and saves space on your screen), the second button switches to an oscilloscope type of display, and the third button will show a frequency display. The fourth button lets you see the parameter amount as you make changes.

Besides the displays doing the jobs they were intended for, they can also be handy for making sure you’ve got it all hooked up correctly. If there is nothing appearing in the display when notes are played, you might have to check and make sure you have some sort of signal passing through.

Another way to get even more feedback is to switch on the “Show Modulation” function. This will make any knobs turn if they are set to be modulated, (e.g.) if an LFO is affecting filter cutoff, you’d then see the cutoff knob turning by itself. 

Connecting the modules together is very easy. Hold the Ctrl key, click on the name of the module in the bar at the top, and then click on another module.  If you want to modulate a certain control, do the same thing, but when you click the destination module, you just click on the knob you want to connect to, such as pulse width or the filter cutoff control, etc.


Generator modules

I won’t go over every module in detail, but I wanted to make sure to mention all the Generator modules and say a little about how they work in general. They are at the start of any new preset you create, so I thought they deserved some extra attention.  

Osc1 is an oscillator with saw, square, triangle, ramp, and sine waveforms. Osc2 is similar, but it has two oscillators and also has a few extra features built-in. It has the same waveforms types, but you can detune one of the two oscillators to get a thicker sound, use hard sync, or throw some ring modulation in to the sound.

With the Sampler module, you are able to load in a mono or stereo WAV file. The file can be a single sample, or you could load in multi-samples as well. The SF2 and SFZ formats are supported.  The separate samples can be played individually, but not in combination with each other. There are a couple ways you can switch between the samples; either manually, or you can set a key/velocity setting for each sample. This module has a lot more controls and features, too many to cover them all in this review.

The Additive module lets you design your own waveform, instead of using the standard ones that are in Osc1 and Osc2. In this module, the buttons on the right side switch between the waveform, magnitude, and phase editing displays. Adjusting the harmonics will change the overall sound as you adjust each of their levels, and each harmonic can also have its phase adjusted individually. On top of all this, it is possible to manually draw in your own waveform using the mouse. The module also has separate controls for Phase, Detune, Frequency, and many others.

Using the Pad module, you are able to construct a waveform in a similar way to the Additive module. One of the ways it differs from the Additive module is that each harmonic actually has an effect on many partials at once, and blends the sound nicely. The frequencies are smoothed out, and the phases of the harmonics are randomly changed.  After you have edited it the way you want, it is stored as a wavetable in memory.

The Noise module is pretty much a no-brainer; it creates pink, white, or brown noise, and lets you filter it. They’ve included a low pass and high pass filter, and a “Seed” control which changes the amount of variation in the sound. 

For external audio to make its way into one of your modular creations, you must add an Input module. This is one of the most basic of all the modules, and yet very useful when setting up Synth Modular as an effect instead of a synth. Audio will go in as a stereo signal, and you can change the way it works with the signal using four different mode settings: Stereo, Mono Left, Mono Right, and Mono Left+Right.


Filter, Modulator, and Effect Modules

Synth Modular has many types of modules for filtering audio in your presets. The first four I’ll mention are the SVF (State Variable Filter), Zolzer, Moog, and 303like. If you load any of these filter modules, you’ll notice all the controls are the same. Low Pass, High pass, Band pass and Notch filter types can be selected for each, and there are the standard controls for cutoff, resonance, modulation amount, and keyboard tracking.

They all have a selection for a two or four-pole, except the Moog-type, which has four or eight-pole types. This adjusts how steep the filter cutoff setting will be: A higher pole number equals a steeper amount for the cutoff. 

Formant, Shelving, Comb, All Pass, and Parametric filter types are also available. EQ types are within Synth Modular as well, a ten band (EQ10) and a 31 band (EQ31) are included.


The EQ10 has sliders you can move up and down to increase or decrease the frequencies, and each of them can be modulated. With the 31 band (an analog type of EQ), the bands can’t be modulated, but it is possible to change the bandwidth on each of the bands manually.

The sound can be altered in many different ways using any of the ten Modulator types.  You could select a standard type of LFO (frequency goes up to 100Hz), ADSR envelope, or a Step sequencer. Many controls are included in the sequencer; random, left/right (moves the whole sequence left or right by one step) mirror, flip, shuffle, fill, and tempo.

The HFO type (high frequency oscillator) has speeds up to 16 kHz, and includes an FM mode. For a standard type of FM in your preset, you can use the FM module that is included in the Controller module category.

There is no shortage of effects included with Synth Modular.  They’ve included a delay, reverb, distortion, phaser, chorus/flanger, compressor, pitch shift, and bit shuffle. The pitch shift can get some crazy sounds. I tried this out with an LFO connected to the “Shift” control, added a little delay, and ended up with a great sound-effect type of preset.

Under Control


The main control panel is always there, even if you start a new preset, or you are editing one you have worked on previously. It has controls for loading/saving presets and banks, and user-definable controls are along the bottom of the panel. There are 32 controls available, and each of them can easily be assigned to a parameter.

This makes it a breeze to get at certain controls, and gives you a way to organize the more important ones in one spot. It’s a very handy feature, as no matter how complex your modular preset might end up, the controls you use the most can be easily accessible.

To use the controls, just right-click on a knob or slider for a module, such as the rate knob for an LFO, go to “Control” in the menu that appears, and then select one of the 32 available slots. You will see the word “Rate” appear above the selected control. You could also assign that same control to a MIDI control on your MIDI keyboard; just right-click the knob on the control panel, and select “Assign MIDI control”.  



Towards the end of my reviews, I usually will go over some additional features about the software I am reviewing. This review is no exception, as this modular synth has so much included, I could go on for days!  I’d have to write a book to go over all the modules and every feature that it has.

Modules can easily be cloned, replaced with other types of modules, or deleted. A simple right-click on the top bar of the module will bring up the menu to accomplish these tasks. Also, saving a preset of the settings for individual modules is done from here as well. After you have the module set the way you’d like, right-click the bar at the top, go to “Presets”, then “Save Preset”.  You then can give it a name, and just click “OK”.

Another feature I like about Synth Modular is that it’s skin-able, and ships with three different skins to choose from. Speaking of how it looks, even the cables themselves can be changed. Just right-click on a blank area of the screen, and a menu with a number of extra options will appear. Under “Options/Wire Appearance”, there are three different types of cables for you to pick from.

Synth Modular has over 1,300 presets included, and they are arranged into various banks. Besides reading the manual, checking out those presets can help you learn how to build your own modular masterpiece.

The CPU usage was pretty good on my older PC, but some of the more complex presets almost pushed it to the edge. It just depends on how complicated the preset is; if you have a lot of modules loaded, and a good amount of modulation going on between them, then of course the CPU use can get a little high.

I really like KarmaFX’s Synth Modular.  It is very powerful, has a great sound, and includes an abundance of presets. Its large number of module types can create nearly any preset you can think up. To top it off, I think it’s much easier to use than many of the other modular synthesizer plugins out there.

It is priced at $112 USD.  If you already own Synth Modular for the PC, and would like to get another license for a Mac that you may own, it is $56 USD. 

There is a 30-day demo version available on their website. They also have extra presets there, and videos showing some of the ways Synth Modular can be used. You can download the demo and buy the full version from their site here:

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