Viper aims to deliver the sound characteristics of legendary hardware synthesizers in a virtual format. We can call Viper a Virtual Performance synth, with a vast array of features like: multiple oscillator types with user waveforms, Sync, Frequency Modulation, Ring Modulation, unison up to 8 voices, filter saturation, filter routings, mod matrix, high quality effects, a powerful arpeggiator, and much more!

A lot of time and research has been invested to make the sound engine of Viper capable of delivering a wide array of sounds, everything from smooth, lush pads, huge basses, and powerful leads, typically associated with traditional analog synthesizers. This was achieved with careful coding, experimenting, analysing hardware synths, and using the ear to fine tune the controls. A constant randomization is also active in the synth to slightly alter its sound to mimic electronic components.

The engine is written in optimised code to use as little CPU consumption as possible, while maintaining a high quality sound engine, finding a good balance between the two. The synth automatically turns off any parts that are not used to further reduce CPU usage. Viper also has a smoothing algorithm for its controls to remove the ‘steppyness’ when it goes between values to give that extra polished sound.

Key features:
● Classic Oscillators with user waveforms
● Multisaw (up to 9x Sawtooth waveform)
● Sub Oscillator
● Noise with coloring
● Punch
● Osc Sync, FM, RM
● Unison up to 8 voices
● 2 Zero Delay Feedback filters with Low Pass, High Pass, Band Pass, Band Reject (notch)
● Filter Saturation curves
● 4 Filter routings: Serial 4, Serial 6, Parallel, Split
● 4 Envelopes: Filter Env, Amp Env, Mod 3 and Mod 4
● 3 LFOs with Oscillator shape morphing
● Mod Matrix
● FX:
● Character (analog boost)
● Distortion
● Filter effects: Ring Modulator, Frequency Shifter, Vowel Filter, Comb Filter
● Phaser
● Chorus
● Delay
● Reverb
● Equalizer
● Arpeggiator with user patterns and Midi Out
● Built in Preset browser
● Section locking
● Midi learn
● Resizable GUI


Download demo version:
Demo restrictions: Preset saving is disabled, silence every 60 seconds. (Because of the demo limitations, automation is not available in some hosts, but is fully functional in the retail version)
Requirements: Win 32/64 compatible system with SSE2 (or higher).

User Manual:
The user manual for Viper can be downloaded from here: Viper Manual.pdf

This is a 32 & 64-bit VST for Windows only! All future updates are free!
Please evaluate the demo thoroughly before purchasing!

Why no Mac version?
Unfortunately, FlowStone does not yet support export to AU, Mac VST yet. As soon as FlowStone supports this, the synth will be available in this format.

Free Soundbanks:
Daniel Craighead Trance Access for Viper Vol.1.zip


  • Dylan Loera
    Jan 14, 2019

    Just wanted to say, after using your synth for about 3 months or so now; is it still tonally a game changer of a synth. Once you add wavetable scanning support and if possible custom lfo shape like Serum it will take over the soft synth game. I am blown away by how pure and clean it sounds, yet is gritty and fat when it needs to be. It really makes other of the top synths sound thin and weak.

    • Adam Szabo
      Jan 15, 2019

      Thank you! Yes, wavetable oscillators will be implemented in the future so it will be even more versatile!

  • AndyF
    Jan 16, 2019

    Very impressive! Ive owned both Virus B + C models in the past and felt instantly at home programming sounds with Viper. One feature request i’d like to see would be an FX version (like Xfer Serum)
    Keep up the good work 🙂

    • Adam Szabo
      Jan 16, 2019

      Thanks, Im glad you like it!

      • Tom Mertens
        Feb 02, 2019

        Oh yes, an FX version would be great. The effects are top notch.

  • raf
    Jan 25, 2019

    Will you add support for virus ti/ti2 presets?

    • Adam Szabo
      Jan 25, 2019

      Its impossible. They are two different synths. Its like asking to open Serum presets in Sylenth1.

      • Dirk
        Apr 07, 2019

        Hmm, i understand her/his question though.
        The point was to recreate a virus right? i recall you even said there could be a possibility to import virus soundbanks.

        • Adam Szabo
          Apr 07, 2019

          The point was to create an emulation, not an actual virus, which is impossible, only Access could do that. I never said it would import Virus soundbanks, there are slight differences in functionality that would just make it not possible. Its like asking to open Serum presets in Sylenth1.

          • Cyberluke
            Apr 07, 2019

            That’s not entirely true. If the plugin would be mapped 1:1 in terms of modules like envelope, filter, FX, mod matrix. Then there are already a lot of librarians on the market. So it would be a matter of loading sysex .midi file from HDD and read this midi messages for the settings of particular preset from a bank. That sounds like a reading custom fxp file and midi is already a standard. It is no proprietary format. Just my little technical analysis

            Czech Republic
          • Adam Szabo
            Apr 07, 2019

            Yes but its not possible to read sysex midi in FlowStone, but if someone figures it out I can give it a try.

          • Alfonso
            Feb 18, 2020

            Any news on this?
            I guess it’d be just a matter of “reverse engineering” the structure of a SysEx file and making Viper read it.

            I might even sell my old Virus.

  • David
    Jan 28, 2019

    Wow, amazing work! Beautiful sound. Looking forward for the mac version.

  • Nicolas Marriott
    Feb 05, 2019

    Absolutely fantasic! It has that special character only the Virus seemed to have. Not sure how you did it but you did.
    Nothing can fill out a mix quiet like the Virus, until Viper came along. Thank you for making this!

  • Giannis Kis
    Mar 01, 2019

    hello!! works with ableton??

    • Adam Szabo
      Mar 02, 2019

      Yes it works with Ableton but only on Windows!

  • Štefan
    Mar 02, 2019

    I owned the HW access virus Ti. Now I’ve tried the Viper demo and I have to say it’s very close to Virus TI. Really good sound, very inspiring. Excellent work Adam.

  • Štefan
    Mar 05, 2019

    Today I bought Viper and I have to say that I am very satisfied. Excellent sound and maximum control convenience. A very inspiring synthesizer. Thank you Adam for your work.

    • Adam Szabo
      Mar 05, 2019

      Thank you for your kind comments, Im glad you like it!

  • Štefan
    Mar 06, 2019

    Adam, I want to ask or plan to do a separate reverb and delay from Viper. Beautiful reverb and delay. I would buy them right away.

    • Adam Szabo
      Mar 06, 2019

      Yes I will do a separate free reverb from it later in the year 😉

  • Štefan
    Mar 06, 2019

    Thank you Adam 🙂 I am very happy.

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