SPC Plugins ArcSyn Synthesizer Review


I check the Instruments forum at KVR semi-regularly to look for new synths, and ones like ArcSyn are the reason why. Clicking on the new product announcements, reading the blurbs and feature lists, you never quite know what you’re going to discover. There, from a company I had not heard of, with a GUI screenshot that looked a little bit awkward (and was drawing some fire from the crowds because of its unusual knobs), was the sort of synth I dream of uncovering. Unassuming, peculiar, powerful… a labyrinth of possibilities.

So here’s my best attempt at summarizing ArcSyn. It’s experimental, seemingly taking its inspiration from the world of modular synthesis, but packaging it into small, selectable oscillator, filter and modulation units within a conventional subtractive architecture. It’s also an absolute modulation beast – more on that later…

Oscillator Scintillator

There are 71 waveforms, most of which are complex processes with a single parameter allowing timbral variation or interactions between several internal oscillators. Here you can find the usual saws and PWM waves, but also bipolar pulse waves, wave-folded triangles, various forms of phase distortion (saw to triangle, variable duty cycle saw, etc.), digital bit-pattern noises, stacked oscillators, sub-octave generators, fixed formant oscillators, 8-bit wavetables, pulse dividers… the list goes on.

There are three of these oscillators, and while they may not interact with each other, they can be layered, detuned and sent to two filter busses, allowing the creation of a vast number of textures that would need much more than three oscillators to create normally.

Looking at the two identical filters, there are regular and “SEM”-style filters of every kind, the latter having a sweet, sticky resonance and going easier on the CPU when making slow pads. There are comb filters, pitch shifters, ring modulators and aliasing generators. There are also some things I’ve never heard of, such as the “repeater” which is basically like a buffer repeat effect, only it can go audio-rate and track pitch, mangling spectra without remorse. It’ll turn a bare sawtooth into an aural representation of a chainsaw on fire.

Lo-fi is also thoroughly represented in the filters and effects, with several types of aliasing available, including linear interpolation, slew limiting, multi-stage down-samplers in series (for that extra phasey crunch), and much more. If you like lo-fi sounds, it’s here in every conceivable flavour.

Pushing The Envelope

So, the generators and modifiers are correct and present, but that’s only half the battle. Every good synth needs a good set of modulation sources. In Arcsyn there are four AHDSR envelopes with adjustable curves, plus 8 LFOs. But these LFOs are not your daddy’s LFOs. I don’t even feel comfortable calling them LFOs, because these are basically modulation heaven made real.

Each LFO shape can be constructed out of up to 16 segments of equal length, and these segments can be chosen from a menu of about 50 pieces, many of which have their own parameter that lets you more specifically tailor its shape. Variable ramps, staircases, curves, bit-patterns, gates, can all be placed in sequence and adjusted until just so. Every step has an adjustable offset and modulation amount, allowing you to smoothly connect any two steps to create a larger, flowing modulation shape, or you can make it as jagged as you like. You are in control, and if you want to relinquish some of it, there are plenty of LFO segments with randomness built into them.

I don’t want to understate this. These LFOs are amazing. You can use them to make acid lines, complete with slides and accents, you can create any rhythmic pattern you can think of, in a way that’s more fun and intuitive than flexible n-point envelopes. You can add really odd, experimental segments such as a binary counter which outputs a different poly-pulse each time it’s triggered, averaging steps, modular arithmetic counters, fractal shapes, frequency modulated ramps… The LFO can also run, like an old analog sequencer, in any direction or jump around randomly. The only word I can think of is “bonkers”!

Even the old-fashioned modulation matrix has plenty of tricks up its sleeve. Each of its 16 slots can feature logic, comparisons, smoothing, bit operations, and other operations between two modulation sources, plus they can pluck a value from a previous slot for very complicated programming. There’s no visual editing, fancy graphics feedback, or clicking and dragging to assign, just plenty of brute force power for your experiments. You can even quantize modulation results to various scales, allowing a fun way to get into aleatory music composition.

The Big Picture

Enough fine details, how about overall sound quality? ArcSyn is internally oversampled by at least four times, in some cases more, depending on the filters and oscillators you select. Its sound quality is very good, with complex modulations holding their own and high, modulated notes free from aliasing, even with sync and ring-modulation effects. All of the waveforms roll off at around 17k, but are consistent in tone, giving the oscillators and filters a warm, almost analog-style sound quality.

The GUI is well laid out but looks a bit ugly. I don’t care – I was having too much fun making crazy sounds! I did run into a couple of bugs during the course of my review, which have very promptly been fixed by the developer. I would have liked to have seen keysync (phase reset at note-on) for the oscillators, but this is a minor point. Obviously more oscillator interactions, FM and the like, would be most welcome, but these would make the CPU load higher, and aren’t as sorely needed as they would be on a synth with static waveforms. As it is, there is so much to explore and a very solid framework for discovering it.

More info: ArcSyn (product page)
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ArcSyn Synthesizer Review


ArcSyn is experimental, seemingly taking its inspiration from the world of modular synthesis, but packaging it into small, selectable oscillator, filter and modulation units within a conventional subtractive architecture. It's also an absolute modulation beast.

  • Features
  • Workflow
  • Stability
  • Design
  • Sound
  • Pricing
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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.


  1. BTW, I am not sure I stressed this enough in the review, but this synth has the BEST LFOs in the world. And there are 8 of them. For those of you familiar with Massive, imagine the Performer module as the world’s finest athlete. A good comparison would be that these LFOs are the T-1000.

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