Nonlinear Labs C15 Synthesizer Update Doubles Polyphony, Adds Polyphonic Aftertouch Support

At the 2025 NAMM Show, being held Jan 21–25 in Anaheim, CA, , Nonlinear Labs is previewing an update to the firmware of their C15 synthesizer that doubles the instrument’s polyphony, adds new options for expressive control and more.

The C15 is performance-oriented synth, designed for playability and detailed sound editing. The digital synthesis engine is based on phase modulation, a comb filter, and a feedback structure, giving the C15 a unique character.

Here’s what’s new in the upcoming Nonlinear Labs C15 firmware update:

  • The polyphony will be increased from 24 to 48 voices, at the previous sample rate of 48 kHz. Alternatively, a higher sample rate of 96 kHz with 24 voices can be used.
  • The C15 audio engine has been expanded to support polyphonic modulation sources. In the first step, polyphonic aftertouch can now be received via MIDI.
  • Pitch bend and sustain functions can now also be used independently of macro controls, freeing them up for other modulations.
  • A sostenuto pedal function and the ability to switch presets and banks via footswitch have also been added.
  • There are also a number of improvements to user-friendliness and optimizations to the operating system.

Nonlinear Labs C15 2025 Firmware Update Overview Video:

Topics covered in the video:

00:00 Intro
00:32 Global Pitch Bend Parameter
00:47 Global Sustain & Sostenuto
01:12 Footswitch to change Presets
01:28 96kHz Sample Rate
01:43 48 Voice Polyphony
02:02 Improved Internal Recorder
02:33 Graphical UI – new Zoom Buttons
02:44 Polyphonic Aftertouch via MIDI
04:11 Copy Modulation Assignments
04:26 Copy Hardware Source Assignments & Amounts
04:41 Summary

C15 Audio Demos:

Details on the new firmware are available at the Nonlinear Labs site.

20 thoughts on “Nonlinear Labs C15 Synthesizer Update Doubles Polyphony, Adds Polyphonic Aftertouch Support

  1. I do not understand the logic of building such a deep, highly editable synth and then giving it only one knob. If you want to actually explore the synth in a free way, you have to add and configure an external knob/fader box. It sounds great but seems like absolute misery to program.

    1. This is a pretty common comment by people who have not used the C15. More knobs would not be useful, and programming muscle memory comes easier on the C15 than many complex knob-laden synths. There are hundreds of parameters on this synthesizer. Even just one envelope would need at least 6 knobs, and those knobs would still have to do double duty for some functions. There are 3 envelopes (doubled across a second layer). Every knob would need LED rings around it, or an LED screen above it. Otherwise you’re looking at a middle screen while turning knobs on the far left. Every knob would need to be extremely high resolution, since there are thousands of steps in every parameter. Even with all of that, I am not convinced the experience would be better, though it would certainly make an already expensive (and heavy) instrument more expensive (and heavier).

      The 8 hardware macro controllers are more than enough. That is quite literally like having 8 morphable presets on every patch.

      As for the update – 48 voice polyphony is a dream come true. Wild things are now possible with unison and layers.

      1. Yeah I don’t buy that. I did not suggest a knob for every function, but I do know many other synths manage to give plenty of hands-on control with anywhere from 8 to 40 knobs. I also know that I like to explore sonic parameter space by twisting two or more knobs at once, rather than constantly being in a modal frame where I can only adjust one parameter at once.

        If you like the the interface that’s great, I’m explaing what I dislike about it and why I found it unpleasant to use.

        1. You can adjust 100s of parameters at once with two massive touch strips (four virtual), four expression pedals (or any combination of expression pedals, continuous sustain pedals, and footswitches), aftertouch and pitchbend.

          Your original post says “It seems like absolute misery to program” which implies you have not programmed it. I am speaking from years of C15 programming experience. No instrument is for everyone, but your concern about only adjusting one parameter at once is simply not true, and I maintain that the fastest, most economical way to program this particular instrument is the one central knob approach, together with 100+ switches and the 10 hardware macro controllers.

      2. [Every knob would need LED rings around it, or an LED screen above it. ]

        How this is done was beautifully demonstrated by Clavia’s Nord Lead 3 (LED rings that even show modulations) and the John Bowen Solaris (LCD strip above all knobs), respectively.

        To defend a pre-historic parameter/value-style UI in 2025 seems rather silly.

        1. I am not defending anything, I am sharing my experience. I have had plenty of knob-laden synths*, and my experience with C15 is superior to them all.

          I had the Nord Lead 3, and the UI was great. Unfortunately, those LED rings failed, and the overall sound quality was lacking. Great synthesis options, though, and I liked a lot about it.

          The only one synth I enjoyed programming as much as the C15 is the DSI Pro-2, which is complex for a monosynth, but is still just a monosynth. Even on that, it seems everyone’s experience was using the four knobs above the OLED screen more than the dedicated (usually multi-function) knobs elsewhere. When I first got the C15, I wished it had something similar (a handful of knobs whose function would change depending on what area of the synth I was programming). After getting familiar with the architecture, I realized this would require considerably more mental gymnastics, because a C15 oscillator is much more than shape, tuning, pulsewidth, etc.

          Here is a flow diagram for the synth engine. Notice the arrows pointing back into the engine from all the different blocks. https://www.nonlinear-labs.de/product/synth-engine/synth_engine_detail.html

          *Pro 2, Nord Lead 3, Nord Lead 4, Virus TI2, Arturia Origin, System-8, MS2000, Prophet 08. Even the Korg OpSix, which is supposed to simplify FM with knobs and faders for every operator/carrier – I can’t imagine that working on the C15 (and I’d argue it doesn’t work well ont he OpSix either). Faders would have to be extremely long, and potentiometers would have to be incredibly precise – there are 1000s of steps in nearly every C15 parameter.

    2. Have you tried a Synclavier ever in your life? I’m going to assume not, but the C15’s interface follows a rather similar idea. The singular knob might on paper look weird, but it works extremely well for a complex instrument like this. Having had the exact same worry as you about it, I can assure you it is really fast to work with.

  2. I haven’t tried it yet. But I rarely turn more than one knob at once, and also knobs are usually in the wrong position on a preset synth. So perhaps this is ok.

  3. this used to be advertised as “players synth”.
    these days it looks old: a single data entry dial, no polyaftertouch and no mpe, not exactly sexy for the 4000€ plus they are asking for.

  4. Isn’t it a bit strange that a simple firmware update can double the polyphony? Why wasn’t it there in the first place if the synth already had enough processing power to allow it? It’s not like a new function is being implemented or something…

    1. “Isn’t it a bit strange that a simple firmware update can double the polyphony?”

      No, it’s commom now for companies to invest in optimizations and feature enhancements after products are successful. See Elektron, Novation & Korg for examples of this.

      “Why wasn’t it there in the first place if the synth already had enough processing power to allow it?”

      Forward-thinking manufacturers will avoid ‘maxing out’ processors until they see how products are actually used by musicians. This minimized the likelihood of ‘glitchiness’, but more importantly means that they can add the features that buyers actually value the most. On this instrument, it’s additional polyphony, but on the Novation Circuit and Elektron devices, it was deeper sequencing capabilities.

      I think it’s awesome when companies do this to devices I own, because you end up getting a lot more than you originally paid for.

  5. That new designer patch bank shuts down any complaints, to my ear. Its an astounding instrument you only buy if you’re ready to seriously embrace it, so I don’t see the one knob as a drawback. It seems sensible for the mindset required. Its not a Minimoog; its more of a starship. Totally differing approaches.

    There should be no Reverb dot com in this thing’s future. Its more like a family heirloom or lofty inheritance. It costs 3614 pounds in black wood; no Volca action here! You can’t measure it with the same stick used to gauge stage pianos or most synthesizers.

  6. I would never look at a synth without a poly aftertouch keybed these days. If Behringer can do it, so can you. Pay the little extra for FATAR at least, these prices deserve poly aftertouch.

    1. Per founder Stephan Schmitt, fwiw: “Fatar does not offer this keybed with poly aftertouch. They have PAT-versions of other keybeds with shorter keys, that do not feel as good as the ones in the C15.”

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