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Rhizomatic Software Plasmonic Physical Modeling/Subtractive Synth – Exclusive Synth and Software Review



What would it sound like if you created a synth that combines sampling, physical modeling, and subtractive synthesis? Marty Cutler finds out.

Rhizomatic Plasmonic is a hybrid synthesizer combining subtractive wavetable synthesis with waveguide-based physical modeling.

Digital Modeling has become fairly common in synthesis these days, but as with sampling, it has expanded well beyond replicating physical instruments. The art and science of sampling has evolved well beyond realistic snapshots of sound into the creation of impressionistic sonic paintings that evolve and change in ways that literal interpretations of sampled instruments never could.

A superb example of sampling veering off-course into other dimensions is Native Instruments’ Absynth, which brought a wealth of creatively edited samples into a deep matrix of modulation, intriguing rabbit holes of DSP, and a flexible, semi-modular environment. The resulting timbres range from dense, distorted tones to gauzy, animated washes and bizarre, metallic sweeps, all steeped in a ton of motion. Absynth continues to be an in-demand synthesizer for sound designers, film scoring, and just about anything that calls for evocative or unusual sounds.

It’s no coincidence that Plasmonic is the brainchild of Absynth’s creator, Brian Clevinger.

As with Absynth, samples are only the starting point; you’re not likely to find faithful renditions of pianos, brass, or any of the typical fare of sample libraries. What you will find are swirling, evolving sounds with pointillistic, floating harmonics and rhythmic undercurrents – almost all of which are gracefully modulated – especially if you are using an MPE-ready controller. 

Under the hood, the synthesis engines drive Plasmonic’s library of wavetables derived from various synthesis techniques: FM, Additive, and the like.

A pull-down menu reveals Plasmonic’s list of available wavetables.

You’ll find the usual subtractive synthesis mechanisms of oscillators, filters, envelope generators, and the like, but you don’t have to dig much deeper before you realize that this is the very surface of Plasmonic’s sound-shaping tools.

In addition to filters, the oscillators and the filters can be shaped through resonators, providing a convolution/physical-modeling approach to sound shaping.

You can choose from a menu of samples, which serve as impulse responses (there is no provision for importing user samples). These short transients superimpose very natural-sounding acoustic characteristics on the oscillators.

Still, there’s much more to Plasmonic’s capabilities; we’ve hardly entered the wormhole.

Oscillators provide digitally-generated wavetables. You can alter an oscillator’s Shape, Symmetry, and Fold. Fold adds buzzy, nasal characteristics similar to oscillator sync, but without the need for a second oscillator.

It’s worth mentioning that Plasmonic offers a unique system for changing values: clicking and dragging horizontally in a parameter’s rectangle can change values in high-resolution, or coarsely, depending on which side of the rectangle you choose.

You can choose between coarse and fine adjustments based on which side of the parameter field you choose. Here I’m adjusting the Fold parameter, and my edit is reflected in the shape of the waveform.

In many cases a double-click on the parameter lets you enter a value directly. Changing the above parameters animate the waveform’s display, giving you visual as well as audible feedback.

Just below the oscillators, things get more complex and interesting with the Resonator module. Its input and output parameters seem inspired by electric guitar – the Input parameter simulates plucking a string at different positions between bridge and neck, and the manual equates the output parameter with switching pickups.

Both of these can be modulated in a number of ways. You can selectively route input and output for oscillators, the impulse, Filter, and noise modules. Likewise, using the clever three-way Routing Switch you can route sources to the Filter module with a simple point and click.

The routing switch at the center lets you pass signal to and from Plasmonic’s multimode filter.

The Multimode Ladder Filter module offers a generous assortment of modes, including low-, high-, and band-pass with up to 4-pole slopes. You also get serial or parallel combinations of low- and high-pass, each with dual resonance settings. Formant deploy a series of resonators to create vowels with X and Y positions, and you can modulate their frequency to interesting effect, somewhat like sweeping a notch filter.

The effects section is unusual, with Saturation and Warm parameters. Their choices include Warm, Flamed Maple, and Krytron, the latter sounding like full-on distortion.

The two Spaces sections are variations on delay networks. These include Feedback Delay Networks (FDN), which essentially form additional resonators and include a variety of sympathetic resonances.

This pop-up menu in the Spaces module lists a variety of sympathetic-resonance impulses. You can adjust tuning and dynamics, among other parameters.

There is no reverb effect, as such, but the delay networks can easily pass for reverberation. Dialing back the wet signal is readily accessible – and advised, on some patches. My only issues with Plasmonic are minor sound design bugs. Some patches use too much “reverberation,” and a couple of patches were much louder than the others. A little volume balancing would go a long way.

Plasmonic’s modulation capabilities are impressive. For starters, the modulation section on the right side of the instrument hosts four tabs: ADSR, LFO, Expression, and Trigger.

Calling the envelopes ADSR underplays their capabilities. For instance, you can apply curvature to any of the envelope parameters, altering the slope of the modulation.

Plasmonic provides a number of ways to accomplish tasks. If it suits you to lengthen or shorten release time, click and drag the R (for release) in either direction, and a graphic of the release will display your edit.

Similarly, clicking the up or down arrows for sustain will graphically illustrate the edited sustain level. The small gear icon at the bottom right of each parameter opens a matrix for – among many other things – entering numeric values; scaling the envelope response to velocity; modulation via LFO; assigning an MPE gesture; and much more – specific to the selected parameter.

Here I’ve double-clicked on the first envelope’s attack stage and opened up a generous page of parameters for that single stage. These are available for each stage of each envelope!

You also get eight freely assignable macros. It’s possible to modulate practically anything, in multiple ways.

Setting Plasmonic up for MIDI Polyphonic Expression (MPE) is quick and instantly available in the Performance Settings Panel. (

Patches differ in their responses to MPE gestures. For example, a patch may have a rhythmic element and MPE sliding may increase or decrease the speed of the rhythm from a slow groove to a tremolo. In another patch, sliding modulates both oscillators’ Shape and Fold parameters, imparting dramatic timbral changes.

Other times, pressure may add a metallic overtone. My Keith McMillen K-Board 4 is the perfect expressive complement to Plasmonic. It’s almost as easy to assign controls to my Novation SL51 MKII controller keyboard, albeit without the individual responses of each note.

In addition to MPE capabilities, I especially appreciated the quick setup for other MIDI modes. Any MIDI guitarist who has laboriously set up a patch to respond to MIDI Mode 4 (one monophonic voice per string) will appreciate the radio button that converts Plasmonic into a MIDI guitar-ready instrument.

Plasmonic sounds like nothing you’ve heard before. And yet many patches have a ring of familiarity.

The folder named Acoustic and Hybrid illustrates my point. Baliset – named after a science fiction instrument – starts off sounding like a koto and then blooms into resonant, synth lead timbres.

Bounce is a metallic pad with an envelope modulating a resonator’s frequency, producing unearthly, whistling, bell tones.

HidddenBehindATree uses Modulation (CC1) to alter the Out position and Frequency of the resonator, as well as the shape of a formant filter, creating high-pitched, repetitive taps and chirps.

Or try Embouchure, a monophonic, woodwind-like lead, whose breathy, subtly metallic overtones change with MPE slides.

Often – especially with an MPE controller – the outcome of the sound is somewhat unpredictable. It’s extremely useful for prospective programmers that clicking a small button above a destination or source illuminates its routings and assignments.

One of the most gratifying aspects of  Plasmonic is that – as unfamiliar as the territory may appear initially – playing and coaxing expression from the sounds, as well as tweaking and programming your own patches, is logical and made as easy as possible by a user interface that earnestly tries to encourage expression and sonic exploration. I recommend the instrument highly, and at version 1.0, look forward to further developments.

Plasmonic is available in macOS (10.11 and later) as a standalone, AU, VST3, and for Windows (8 and later) as Standalone and VST3. As yet there is no AAX version.

Price: $149

Plasmonic site here

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