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KV331 Audio SynthMaster

Software Synthesizer
By Paul Nagle

KV331 Audio SynthMaster

SynthMaster might seem like an ambitious name, but then SynthMaster is an ambitious synth...

KV331 Audio have been around since 2004, concentrating on making SynthMaster the best soft synth it can be. Having reached a mature version 2.7, it’s a striking example of how a single product can evolve if given enough time and care.

SynthMaster is a single instrument endowed with almost every established synthesis type, yet it’s an affordable alternative to the industry’s big hitters. From a packed interface, it delivers analogue emulation, wave scanning and vector synthesis, phase modulation, additive synthesis, sample playback and FM. These are yours to mix, mash and modulate in practically any way you see fit. For some, this jack of all trades has been hiding in plain sight for many years — if that includes you, then boo!

Getting Acquainted

For such an ambitiously–named synthesizer, SynthMaster has a fairly small and intense user interface. It isn’t scalable but comes with several skin choices; if you have the time and inclination, an Interface Editor is supplied for making your own. Please try and avoid the rookie mistake I made almost immediately, which was to try an alternative skin without first downloading the manual. Having selected the ‘Player’ option from the Settings menu, there was no obvious way to go back — because the new skin didn’t have a Settings menu! Judging by the FAQ, I’m not the first to have done this, but it wasn’t the best introduction. Incidentally, the manual hasn’t caught up with SynthMaster’s current version yet, so you’ll need to work out some of the latest enhancements for yourself, or check them out in the web site’s tutorial videos.

SynthMaster is available in several cross–platform bundles in VST and AAX formats, plus Audio Units for Logic users. Or there’s an inexpensive Player version with limited editing capabilities but 1100 presets. If you have an iPad, it’s well worth grabbing the free iOS Player app. Just prepare to be tempted to upgrade to the Pro version (which can import user banks).

The free iOS player.The free iOS player.

I mentioned that the interface, with the supplied skins anyway, is packed. It’s also a bit obtuse, not necessarily because of any design flaws or shortcomings, it’s simply that there is a wealth of buttons, many of which juggle the contents of the various boxes. Some, such as the Filter box, offer just two options but if you look underneath, you’ll see 11 buttons each revealing a single LFO, envelope or key–scaler. While this approach keeps the panel compact, it condemns you to an eternal click–fest with no hope of a complete picture of any patch — except in your head. Even when information is visible, it isn’t always optimally placed. For example, it would surely make more sense to show values next to knobs rather than as tiny text in the ‘Parameter Update’ window.

At the top of the panel are six buttons that determine the main view for patch editing and selection. A SynthMaster patch consists of two layers, each with two oscillators, two filters, an arpeggiator and effects, plus voice LFOs, envelopes and modulators. Each patch also has four global LFOs, plus a dual-bus effects system and a mega modulation matrix to bind everything together.

Everything Counts

Purchasers of the ‘Everything’ bundle gain every expansion bank available; this currently totals 28 banks and 1750 presets combined into an easily–searched database. Amongst these, the three volumes entitled ‘Dawn Of Electronic Music’ contain snippets of Kraftwerk, Depeche Mode and Tangerine Dream, complete with sequences, reasonably convincing solo patches, sound effects and basses. Other collections to idle away a few hours include recognisable Jean-Michel Jarre and Vangelis lead patches, Wendy Carlos harpsichords, Tomita whistles and many more. Such sounds inspired me to buy my first synth back in the mists of time but are a treat even if you’re not wallowing in nostalgia. It isn’t just ‘Old Fogey Central’ though; plenty of contemporary dance and electronica patches are present in all their rhythmic, euphoric, MDMA–soaked glory.

Regardless of the bundle you opt for, the presets supply a strong hint that any shortcomings in your own sounds are unlikely to be SynthMaster’s fault.

The patch browser (and an alternate skin).The patch browser (and an alternate skin).

Beyond The Presets

Assuming you’re enthused by the diversity and downright usability of many of the factories, the next stage is probably to try brewing your own. Rather than edit existing patches, I found it preferable to start from scratch with the ‘new’ option. This offers either a plain starting point or a selection of partially–built patches designed as templates with names such as Vektor Bass, Trance Pad and so on. None of these are particularly stunning, but here’s the good bit: any sound tagged in the library with the attribute ‘template’ will be added to the list to serve as a personalised blank slate in future. It’s a simple but effective idea.

Press either of the two layer buttons and SynthMaster shows information related to that layer alone, including a graphical overview of its structure. You can click on modules to activate them, decide if the layer should be polyphonic, whether you need both oscillators, how the filters are arranged and so on. The dual-layer architecture supports layering of monophonic and polyphonic patches, which can be useful to emulate a Hammond organ’s monophonic percussion, for example. While the overview doesn’t show every detail, it’s handy to visualise the audio path, the modulators present and the effects blocks that are enabled. This view can be replaced by the layer’s arpeggiator or effects settings.

The Oscillators

Narrowing our attention to the Osc box, you’ll see it houses two main oscillators and four modulators, but only one can be displayed at once. It’s when you start button–clicking in earnest that you realise SynthMaster has more hidden items than an Amazon tax return. Even the simplest building block — the ‘Basic’ oscillator — isn’t restricted to the usual selection of subtractive waveforms. It’s joined by a plethora of single-cycle digital waves, a collection that can be boosted by importing your own (after suitable preparation). Going further, multiple samples can be imported too, once converted to .SFZ format. Examples are provided, just in case it’s not obvious how incredibly useful these can be. They include Mellotrons (cello, violin, brass, choir and flute), a twangy santoor, bells, shakuhachis, the obligatory breathy vox and many more. Following instructions in the manual I initially failed to create a working .SFZ file but after a word with the helpful chaps at KV331 Audio, I copied a few files manually and all was well.

However you load your Basic oscillator, increasing the voices parameter will generate up to eight copies of it. The extra voices are optionally spread across the stereo spectrum and detuned for that ‘lush richness, no effort’ effect we all appreciate sometimes. The term ‘Basic’ seems way too modest, especially as there’s more oscillator functionality still to take into account. For now, there are other types to cover, starting with Additive, which has eight Basic oscillators — and they don’t need to be copies. A neat little panel contains the waveform, volume, pan, frequency and detune of each. Naturally, this is fab for designing organ patches, but given that each wave has the equivalent choices to a Basic oscillator, Additive is a far more powerful source than it appears.

In contrast, the Vector oscillator is exactly as you’d expect: four Basic oscillators with a vector control to mix them. If you have a joystick or Kaoss pad, a quick application of SynthMaster’s ‘MIDI Learn’ function turns them into performance controllers Wavestation– or Prophet VS–style.

I’m going in! I’m going in!

For the next bite of classic synthesis, the Wavescanning oscillator is a simplified slant on the format. It’s a sequence of up to 16 waveforms inserted then read sequentially, either by a manual action or driven by the usual list of modulators — including multi–stage envelopes. Even if it won’t win the world’s ‘longest wavetable’ trophy, Wavescanning is fun. Lastly, the oscillator can serve as an audio input, turning SynthMaster into an effects processor or vocoder.

Regardless of the oscillator type, it may be subjected to Amplitude Modulation, Phase Modulation or Frequency Modulation. Four mod sources are available to each layer, and these are extra oscillators not far behind the main pair in power. They can act as super–charged sub oscillators, modulators for FM or PM (phase modulation), and they aren’t above modulating each other along the way.

It was becoming clear that the Osc box has more inside it than a Russian doll, but we shouldn’t move on just yet. The easily–overlooked Algorithm menu opens to reveal further nested menus: Spectrum, Bend, Sync and Other. Spectrum adds waveform–level non–resonant filtering, while Bend provides several means of bending the waveform into new shapes. Sync scores firstly by dispensing multiple flavours of spiky, useable sync, and secondly by not costing you an extra oscillator. Finally, anyone fretting that KV331 forgot pulse-width modulation can relax. Admittedly it’s relegated to the ‘Other’ menu along with bit reduction, but on the plus side, the pulse width of any waveform can be varied, not just square. All these processes can be applied to Wavescanning, Additive and Basic oscillator types.


The filters can be configured in series or in parallel, with a third option, split, on hand for individual oscillator processing. Divided into digital and analogue types, the filters are ultra–tweakable; the digital side has comb filters, dual filters and multi–mode filters, while the analogue variants are ‘modelled after the famous ladder filter’. They don’t match the believable analogue sweetness of, say, U–he’s Diva, but in scope they go much further, thanks to a continuously variable slope or the ability to morph smoothly between modes. It’s planned for version 2.8 to extend the modelling to filters of the Roland TB303, Korg MS20 and Oberheim SEM.

Distortion can be positioned before, after or inside the filter and, thanks to a drawable distortion curve, there’s an extraordinary degree of control to delight lovers of edgy, aggressive filtering. The digital filters feature a hard limiter that contains excessive resonance. I particularly liked the dual version, a twin multi–mode offering with seemingly limitless variability. Arguably, the only missing type is some kind of formant filter.

The global effects section has two configurable buses and a single instance of reverb and echo.The global effects section has two configurable buses and a single instance of reverb and echo.


There are two types of effect: layer and global effects. Each layer has three effects boxes containing distortion, a lo–fi processor, ensemble, phaser and EQ. The high-quality ensemble was fresh in my memory from playing the factory string pads; it offers up to eight voices and a pair of LFOs dedicated to modulation of the delay and voice spacing. Its natural partner is the 16 stage stereo phaser — very rich, resonant and Jarre–y.

Complementing the per–layer effects is a dual-bus system comprising echo, reverb, chorus, vocoder, tremolo and two compressors. Since a patch has two layers, both potentially arpeggiating or sequencing, it would have been nice to have a delay for each. However, both the delay and reverb can only be assigned to a single bus. That limitation aside, the effects can be arranged in any order and it’s an indicator of how much we still have to get through that there’s only room to mention that the vocoder is quite excellent.


The diversity of oscillators, filters and effects builds a solid foundation for in–depth programming, so it’s just as well that this is supported by an equally rigorous modulation capability. No fewer than 95 modulation sources and over 650 destinations are quoted — and I’ve no reason to doubt this! Each layer can draw upon four regular and two multistage envelopes, two ‘2D’ envelopes, a pair of LFOs, and four key scalers. The 2D varieties generate two simultaneous outputs — X and Y — that are just the job for mixing Vector oscillator levels.

Key scalers are welcome alternatives to regular modulation curves. One obvious application is to modify parameters differently over certain areas of the keyboard. Actually, key scalers provide the only practical means of creating keyboard splits since this isn’t one of SynthMaster’s core functions (neither is multitimbrality). While they’re no match for the 128 individual levels of, say, U–he’s Bazille, the 22 points given to SynthMaster’s key scalers are about as many as could fit neatly into the available screen space.

Modulation of any parameter is assigned either by right–clicking then trawling the nested menus or by manually adding entries to the matrix. An impressive but shy beast, the modulation matrix spreads its content over eight pages, each with eight entries. It is comprehensive enough to earn SynthMaster its ‘semi–modular’ tag even if some aspects are misleading. For example, when exploring two-operator FM synthesis, I selected an Algorithm of Bend +/–, dynamically skewing the modulating sine wave into a saw. This sounded pretty cool so I next wanted an LFO to do the bending automatically. However, I couldn’t see ‘Bend’ as a modulation destination. Instead, I had to select ‘Phase’ — the name of the parameter if I’d selected Spectrum, not Bend. The same applies to setting up PWM, so hopefully it’s an easy fix for the next update. Since I’m airing wishes, it would be so nice to see at a glance which controls are being modulated. It’s true that if you turn to the matrix, a view filter can narrow down the options by source or destination, but it’s less elegant than it might be.

The four global LFOs.The four global LFOs.

The four global LFOs are equipped with the usual waveforms, plus variable noise content and optional random behaviour. Each can run freely or be synced to the host clock, and if you switch to step or glide mode, the waveforms can be user–sculpted — a great source of complex rhythms.

Perhaps recognising that pages of modulation can be a drag, SynthMaster has eight ‘easy knobs’ and two XY pads assignable as mod sources. The complexity of the synth engine can therefore be hidden away, reduced to the most important parameters needed for live interaction and mapped to your favourite hardware controller. Let’s face it, a control surface big enough for all of SynthMaster’s parameters would fill the room!

Rounding Up

After only a few weeks, all I know for sure is I’ve barely scratched the surface, but I suspect that will remain true after a few months or even years. SynthMaster is bright, in–your–face and capable of clean digital synthesis one moment, dirty, industrial noises or warm, animated pads the next. It has great presence, solid bass and there doesn’t seem much it can’t cover.

Polyphony is set at patch level up to a maximum of 64 voices and you can specify the playback quality at patch level too. Higher settings increase the internal sampling rate and place greater demands on the CPU, but even the draft mode is often quite serviceable. If necessary, you can crank up the resolution of the LFOs and envelopes by increasing the engine buffer size.

I found performance mostly good on my old Mac Pro, at least until I got carried away stacking voices. But when I began in–depth editing I experienced a few crashes (using Logic 10.0.7) and also encountered several bugs. For example, I saved a wavetable I’d made but later, when I tried reloading it, the waves I’d added had been forgotten, replaced by sine waves. Finally, Scala tuning is supported either per preset or globally.


If, like me, you’re curious about the name KV331 Audio, I can report it’s inspired by a Mozart piano sonata (number 11 in A, in particular its ‘Turkish’ final movement). Still confused? Well, Mozart’s works are known by their K or KV numbers after Ludwig Köchel who catalogued them. If that explanation seems excessively geeky it’s possible SynthMaster isn’t for you. At times, it does feel like the work of a committee of geeks, determined to squeeze in every synthesis feature imaginable, regardless of the impact on usability.

Ultimately, despite some operational clunkiness, it’s hard not to marvel at a single plug–in able to tackle vector, additive, wavetable and FM synthesis, plus analogue modelling, phase modulation and sample playback. Its filters are as flexible and fat as a well–oiled Sumo wrestler, the effects are good and the modulation options very good. If you’re a novice or simply unsure where to start, even the cheapest bundle has plenty of factory sounds to sweeten the deal. Whichever way you look at it, SynthMaster is a superb achievement.


With their usual thoroughness, KV331 have kitted out their arpeggiators with the most popular modes and motions of classic synths. Unsurprisingly, there are a few worthwhile extras too, such as arpeggio patterns of up to 32 steps, each with adjustable velocity, slide and length.

If you’ve played around with the Kraftwerk and Tangerine Dream patches, you’ll already know the arpeggiator has a step sequencer mode. Sequences you’ve made in your DAW can be imported directly as MID files, although it’s a good idea to quantize them first.


  • A powerful and mature plug–in bristling with synthesis types.
  • Semi–modular in nature, it features a 64–slot modulation matrix.
  • Versatile effects and powerful filters.
  • Ships with 1100 factory patches with further expansion banks available.
  • Affordable.


  • Interface is dense and not scalable.
  • Some minor operational inconsistencies (eg. naming of modulation matrix entries).
  • Some crashes.
  • Manual needs bringing up to date.


SynthMaster is a semi–modular soft synth with a wide appeal for programming enthusiasts keen on all types of synthesis. While the interface could be better, there’s not much SynthMaster can’t achieve once you know your way round.


Full version $379 (see web site for additional pricing).

Full version $379 (see web site for additional pricing).

Test Spec

  • Mac Pro running OS 10.8.5, 16GB RAM, 2x2.66GHz Quad–Core Intel Xeon running in 64 bit mode.
  • Logic 10.0.7 in 64–bit mode.
Published March 2016