Review: Arturia PolyBrute

OSCILLATORS

PolyBrute’s oscillator section offers a wide tonal pallet and has a few sexy quirks I haven’t seen in more conventional analogue polysynths.

It has dual VCOs typical of Arturia’s ‘Brute Style’ oscillators, each with slight differences, in addition to an independent noise stage. They have independent pathways to either/both VCF1 and VCF2, controlled within the adjacent mixer section.

Common to both is a waveform mixer – the first knob provides a continuous blend from a Sawtooth to a Triangle wave; the second knob blends between the output of the Sawtooth/Triangle blend and a Square wave with variable Pulse Width.

VCO1 includes a wavefolding Metalizer function which adds complex harmonics to the VCO output, having a sonic character heading toward the angular, atonal sound of West Coast-style synthesis at extreme settings. There is also Oscillator Sync (VCO2 to VCO1), but with a unique twist – it is variable and may even be modulated, allowing you to explore the spectrum from Soft to Hard Sync.

VCO2 may also modulate the pitch of VCO1 via the FM 2 to 1 knob, simultaneously with VCO2 to 1 Sync if you like! VCO2 also has a Sub oscillator within, with its control balancing the mix of the Sub with the output of VCO2. Finally, VCO2 may even modulate the cutoff of VCF1 (the Steiner filter) to achieve complex audio-rate modulations for some genuinely chaotic sounds!

A variable Noise generator, independent of the output of VCO1/2, gives a continuous spectrum of noise colours from bright to dark. It may even modulate the cutoff of VCF2 (the Ladder filter).

TRUE ANALOGUE MORPHING

PolyBrute’s most enticing feature is its Morphing capability. Although Morphing has appeared on a handful of DSP virtual analogue synths (starting with Clavia’s ‘Nord Lead’ series back in the ’90s), to the best of my knowledge the PolyBrute is the first proper analogue polysynth to feature it. This is not a mere crossfade between two sounds; it is actual parameter Morphing with the entire workflow of the synth designed to exploit it.

The Morph knob provides continuous movement between Sound A or B and determines which layers your parameter tweaks will affect proportionally. Furthermore, the Morph amount is freely assignable as a destination in the Modulation Matrix. Considering it is such an important control, it’s strange that Arturia didn’t use a larger knob cap to draw focus to it!

Although most parameters are Morphable, those that radically alter the voice structure or are switch-based do not morph (for example, the Timbrality setting controlling the voice assign modes and the Type selection for the DSP effects). Also, Sources and Destinations allocated in the Modulation Matrix must remain consistent between Sound A and B because the Morphing animates the amount of modulation. Notwithstanding such minor limitations, the Morphing feature is an exciting gift to the passionate sound designer, inspiring exploration of harmonically elaborate timbral movements that would be laborious to achieve via other means. In addition, at intermediate travel points of the Morph knob, proportional blend points often reveal sweet spots that you’d rarely set out to program intentionally.

CONVENIENCES A PLENTY

Although depth and complexity are generally the enemies of ease of use (often forcing heaps of menu diving), Arturia has excelled with the inclusion of clever user interface enhancements.

For many front panel parameters you’ll find a circle printed next to the label, indicating additional options that will appear on the display for editing. It’s an intuitive way for Arturia to include scope for extra features without cluttering up the front panel and whilst also minimising deep menu diving. Bravo!

If you want some quick and dirty fun with the Morph function, you can quickly assemble a patch by copying sound A or B from any other patch memories in the machine. This is a fantastic way to hit some happy accidents you’d never consider programming with intention. Of course, there are also parameter randomisation functions that often yield useful results and precipitate satisfying sonic experiments.

The editing conveniences continue with a new Snap Shot function that allows you to roll back to up five editing states should your sound design flights-of-fancy take you on dead-end tangents.

MORPHÉE/RIBBON

The most cosmetically striking aspect of PolyBrute is the Morphée control, arguably inspired by the standalone Touché by Expressive E. It’s a capacitive X/Y control pad with Z control achieved by applying downward pressure, and there’s plenty of travel for expressive power. Touché owners often speak of the virtues of rhythmically ‘bouncing’ the pad on the Z-axis, simulating the feel of side-chain pumped pads typified by modern pop/EDM genres. However, the Morphée goes further than a mere XYZ controller. It also has a mode to interact with the Arp/Seq (borrowing from MicroFreak’s Spice/Dice/Ratcheting functions) and a Morph mode. I found it required some initial practice to achieve the precision I wanted, but I acclimated quickly and loved it after a few sessions.

A Ribbon Controller spans the area immediately above the keyboard. While its inclusion is welcome it doesn’t extend the keyboard’s entire length, which would have been preferable (particularly when mapped to control pitch, allowing the keys to provide a visual guide for notes).

DUAL FILTER SECTION

The Dual-VCF section of the MatrixBrute remains, providing an abundance of character and tonal variation. Configurable in series, parallel or a blend of both, it’s a highlight of the original – except we now have independent filter circuits per voice!

VCF1 is Arturia’s trademark multi-mode 12dB/octave Steiner-Parker filter, including ‘Brute Factor’ – essentially a variable feedback circuit that imparts insanely savage overdrive at extremes and subdued overtones at lower settings.

VCF2 is a fruity, dark-sounding 24dB/octave ladder filter that, unlike traditional ladder filters, preserves low-frequency content with increasing resonance. As a result, the PolyBrute is capable of ridiculously earth-shaking monophonic bass patches! There is also an integrated overdrive stage, which exaggerates harmonic sweet spots as the filter is swept.

MODULATION MANIA

Donning a trio of ADSR envelopes and a trio of LFOs, the PolyBrute is ready for prime-time sound design delights.

The first two envelopes, VCF ENV and VCA ENV, are traditional ADSR envelopes (remapped if desired). The third envelope, MOD ENV, is also a conventional ADSR envelope with an adjustable onset delay, freely assignable. The Envelopes are loopable – either twice, three times or infinitely – thus, they become additional LFOs if desired; used with short time periods for each stage, they’re capable of audio-rate modulation effects!

The first two LFOs offer several shapes and are polyphonic, each syncable in various ways with different retriggering modes. LFO1 adds a Phase start adjustment whilst LFO2 provides control of delayed onset. The third LFO is unique, providing continuous adjustment to the curve slope (for both the rise and fall stages), with Symmetry proportionally adjusting the rise and fall periods. By default it operates monophonically, but by engaging ReTrig mode it behaves polyphonically. The Single-mode for this LFO plays the LFO once, effectively providing an additional Attack/Decay envelope. In tandem with the Slope/Symmetry controls, LFO3 is ideal for creating synthetic percussion patches where slope adjustment is critical. A fourth ‘hidden’ LFO is also available, hard-wired to vibrato, reassignable in the Modulation Matrix.

Additionally, there is a custom modulation source, the ‘Motion Recorder’, effectively acting as a DIY envelope/LFO. The movement of any front panel knob can be quickly recorded and played back either once or looped. Although only one Motion Recorder is available in a patch, it can simultaneously affect multiple destinations in a macro fashion via the Modulation Matrix.

MODULATION MATRIX, EXPANDED

To the casual observer the PolyBrute’s Modulation Matrix may appear less extensive than the MatrixBrute’s, but there’s more here than meets the eye…

The MatrixBrute has a 16×16 array of buttons translating to 16 destinations (columns) and 16 sources (rows), but that is the limit. Furthermore, its first 12 destinations are hard-wired as labelled, with only the remaining four slots being freely assignable.

The PolyBrute is a different animal. While it presents its matrix on a smaller 8×12 array of buttons, there are now four pages of these eight destinations available (thus 32 in total), and every destination slot is freely assignable. Like the MatrixBrute, modulation connections can be modulated by other modulators in a multiplicative manner, and the maximum limit is now a generous 64 connections overall.

When you consider the numerous opportunities for audio-rate modulation, particularly with the looping modes of the envelopes, and that the Morph transition point can be modulated by anything, the mind boggles at the possibilities and the engineering marvel of the sheer number of parameters that can undergo such modulation simultaneously!

POLYBRUTE CONNECT

If the PolyBrute’s ability to Morph sounds in the analogue domain doesn’t impress enough, the included Editor/Librarian software undoubtedly seals the deal – particularly for those with a DAW-centric workflow.

‘PolyBrute Connect’ is a deep Editor/Librarian that runs as an AU/VST/AAX plugin or a standalone application and provides a precise bi-directional interaction with the synth. Since the PolyBrute’s display doesn’t show stored parameter values while tweaking knobs, the software offers a more confident editing experience – particularly when alternating between editing Sound A or B within a patch. Better still, whilst manipulating the front panel Morph knobs, you’ll see the parameters update in real-time as you tweak. Finally, it’s within this editor that you have a means of fine-tuning the start and endpoints of Morphed parameters, in addition to the editing conveniences you’d expect from a full-featured editor.

When launched as a plugin within a DAW MIDI track, PolyBrute Connect acts as a MIDI bridge presenting all parameters as automation hooks to the host DAW. Behind the scenes, communication between the PolyBrute and the software uses high-resolution 14-bit MIDI RPN CC data (rather than coarse 7-bit CC data), so the convenience this offers can’t be understated. It’s much more intuitive to edit pre-labelled lanes of automation in a DAW rather than triple-byte MIDI RPN data, which most DAWs handle quite poorly!

Better still, if you print to audio tracks in your DAW as you progress, multitracking the synth with complete round-trip editing is easily achieved by launching new instances of PolyBrute Connect. Each instance independently stores patches within your DAW project. By revisiting previously tracked elements and clicking the ‘Activate’ button in PolyBrute Connect, the patch state is recalled on the synth independent of the patch memories.

The user experience is an Editor/Librarian that works as fluidly as you could ever want. Rather than developed as an afterthought, it’s evident that PolyBrute Connect’s development happened in tandem with the synth – otherwise, this level of integration would not be possible. I’ve little doubt existing MatrixBrute owners will be envious of the workflow it provides.

EFFECTS

When I reviewed the MatrixBrute in mid-2017, its analogue effect section underwhelmed me. While not being a deal-breaker (we’re spoiled for choice in the DAW universe), it was the Achilles’ Heel of an otherwise excellent synth in a standalone context.

Thankfully, Arturia has included a proper stereo DSP effects engine in the PolyBrute. Three effects blocks are available – Modulation, Delay and Reverb – which may run as inserts or sends. In addition, a handy global bypass button provides a true analogue signal path to satisfy analogue purists.

The Modulation effects include Chorus and Phaser and seven supplementary ‘Alt’ types including Flangers, other Phaser/Flanger variants and, unexpectedly, sonically destructive types like Bit Crushing and Down Sampling. The Chorus and Phaser sound particularly excellent, whilst the destructive effects provide fodder for more exotic sounds – especially once you’ve applied modulation. Yes, you heard me right – parameters within the effect engines (except Effect Type selection) are destinations available within the Modulation Matrix, and they are Morphable!

The Delay section extends well beyond the MatrixBrute’s BBD, however it is still present. Nine variations are provided including a Karplus variant, comprehensive clocking options and a post-effect filter section, fantastic for controlling the tone of the repeats. While I had hoped to modulate the delay taps, what’s on offer here is a massive improvement.

The Reverb is spectacular, providing massive decay times with smooth tails without any hint of cyclic metallic ringing. Several types are available, and a cleverly implemented post-effect filtering section helps tame the tails. Expect everything from subtle spatial room treatments to outlandish supernatural dreamy shimmers, and everything in-between!

STEP SEQUENCER / ARPEGGIATOR

While I prefer sequencing within a DAW, the Sequencer and Arpeggiator functions of the MatrixBrute have been further refined for the PolyBrute. It’s now polyphonic, and Arturia has added some intriguing randomisation and editing functions that were perhaps inspired by the MicroFreak. A unique Matrix Arpeggiator mode facilitates the creation of complex arpeggios via the editing matrix (up to 32 steps in length), extending the possibilities of arpeggiated performance. Whilst performing with the Arpeggiator, if you want to preserve what you’re hearing you can convert it into a sequence for further editing and changing up the rhythmic character on the editing matrix. Combined with the Morphée mode that interacts with the Sequencer, there’s much potential here to spark fresh ideas.

In addition to Step Sequencing, you may record sequences in real-time, and there’s a handy metronome that elevates the usability of this approach. Modulation tracks allow automation of up to three knob-based parameters, providing yet another means to impart textural movement in your patches.

COMPLAINTS DEPARTMENT

Six voices is a bit limited for Arturia’s debut flagship polyphonic analogue synth, considering the Split/Layer facilities on offer. I found myself frequently reaching the voice limit when playing layered/split patches and also when playing patches with lengthy release times, resulting in voice stealing (albeit a pleasing effect when invoked intentionally as a stylistic effect). Although it would elevate the cost, I’d speculate that there’s a market for a 12-voice model and perhaps Arturia might someday agree.

The Step Sequencer would benefit from having more than three Modulation Sequence lanes. Thankfully, the opportunities for modulation elsewhere in the synth are copious, and the potential for their chaotic interplay, in tandem with the convenient automation of any parameter via the PolyBrute Connect plugin in a DAW, adequately compensates for this.

Before getting up and running with PolyBrute Connect, there are a few hoops to navigate. It’s necessary to create an Arturia user account, register the PolyBrute’s serial number, install Arturia’s Software Centre App, download software, and then activate it. I don’t understand the need to Activate the software – it is of no use without a PolyBrute attached, and the mere presence of the unit attached should be proof enough of entitlement to use it!

Whilst the PolyBrute is an engineering marvel, some aspects of the MatrixBrute are missing in action. For example, MatrixBrute’s four white Macro knobs: each allowed ganged adjustment of up to 16 parameters (having independent ranges and polarity), making them brilliant as ‘serving suggestions’ of ideal interaction points with a patch and even provided a primitive Morphing implementation (four times over).

Those familiar with the MatrixBrute will notice that its extensive array of rear panel input/output jacks (intended for integration with Eurorack modular rigs) is absent on the PolyBrute. In the context of a polyphonic synth, this is understandable considering the technical complications it would present.

And again, the omission of the MatrixBrute’s tilting front panel is not to be discounted!

SUMMARY

In recent years, several modern analogue polysynths I’ve reviewed have fallen short of the mark. Often, they’ve had underwhelming oscillator sections, minimal modulation facilities, or lacked essential fundamentals (like Aftertouch or a decent keybed). Of course, such products don’t command the price of the PolyBrute, but maybe that’s why we frequently see a deluge of ‘built to a price point’ gear on used trading groups. True synth fans rarely sell off absolute treasures unless circumstances demand so.

While its build quality is slightly less polished, the PolyBrute delivers a true six-voice analogue polysynth with unique Morphing and extensive modulation capabilities – for not much more than you’d pay for the MatrixBrute. It vastly eclipsed any expectations I had for the polyphonic MatrixBrute of my dreams. Although its price point puts it alongside Moog, DSI/Sequential and extensive bespoke Eurorack systems, its advanced modulation, Morphing feature and the depth of integration offered by the PolyBrute Connect plugin/app herald Arturia’s coming of age in the high-end synth market. If there is ever a synth you’d consolidate your rig of lesser items for, this would be it!

It is fantastic value for money, even with its mere six-voice polyphony. Its unparalleled ability to morph and contort those voices in so many creative ways, in a package that’s so intuitive with minimal menu diving, has pushed this dream machine to the front of the pack. In the hands of a skilled and imaginative sound designer, it’s an undeniable weapon that is bound to inspire the most demanding analogue synth aficionado for years ahead.

Aside from shelling out for an extensive Eurorack modular synth rig (which would lack polyphony and recall), there aren’t any non-modular analogue synths that reach PolyBrute’s sonic pallet. So although Arturia made a false start with their ambitious yet ill-fated Origin DSP modular from 12 years ago, they can now legitimately claim the crown for engineering the most innovative and desirable polyphonic analogue synth in recent years.

Congratulations, Arturia! You’ve not only delivered a head-turning piece of elite engineering, but you’ve also provided a complete experience without teasing us with essentials like ‘PolyBrute Connect’ that are “coming soon…”