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


  • Jordan
    Mar 13, 2020

    Every time I try to download the demo version, the download keeps on failing. Is there any other way to get the demo to download?

    • Adam Szabo
      Mar 13, 2020

      Perhaps you need to temporarily disable any anti virus running in the background until you download it.

    • Troy Wilson
      Apr 05, 2020

      I had the same issue, tried a whole lot of things, what ended up working was instead of clicking the demo download link directly ,try RIGHT clicking the link and choosing the option “Save Link As” and it should complete the download…Hope that works out for you

      • Products Explorer
        May 24, 2020

        no problem with download, check if popup is not blocked by browser. I have problem with all downloads because of this issue.

  • Luís
    Mar 13, 2020

    Is there anyway to run It on Mac?

    • Adam Szabo
      Mar 13, 2020

      Not that I know of

    • Dremix
      Mar 28, 2020

      Have a look at DDMF Metaplugin. You should be able to run Viper on Mac with it. Download both the Metaplugin demo and Viper demo and try it out.

      • Adam Szabo
        Mar 28, 2020

        No it does not work. DDMF Metaplugin only loads Mac vts and not Windows ones. You cant do the reverse either, so running Mac Au on PC

  • Jonathan
    Apr 01, 2020

    It would be great if you make a stay at home sale, but I can imagine that these times are hard for you as well. I just wanted to buy viper this month, but money is a little more tight right now. But I’ll definitely buy Viper this year! I liked the demo so much that I even started to learn sounddesign just for this synth (and maybe rapid, and a real virus if I have more money one day haha)

    • Pieter
      Apr 22, 2020

      Would love a discount to ill buy it right away.

  • Status Red
    Apr 03, 2020

    The newest version crashes the host when I’m switching presets (it takes several clicks) while playing the track/pattern (Ableton 10.1 and FL Studio 20.1.6, Win10 64bit).

    • Adam Szabo
      Apr 03, 2020

      Yes thank you, there will be a new free update very shortly which will fix this

  • Ivo Andreev
    Apr 07, 2020

    Really great synth that sounds amazing under Windows! Along with this virus and the reduced budget, somehow Viper stayed out of my radar so buying will wait… But when I buy it I’ll ask for a black skin too (nothing against red) or at least an opportunity to do it myself (under Windows 🙂 Be healthy and still creative!
    P.S. Maybe VIENNA ENSEMBLE PRO will solve the Mac problems 🙂

  • Gis
    Apr 19, 2020

    Hey Adam,
    Just found about these vst’s 🙂
    Can Viper produce the same sounds as your JP6K synth?
    I’m looking for those typical JP8000 saws

    • Adam Szabo
      Apr 19, 2020

      Hey, yes, Viper can do very similar sounds with the Multisaw Oscillators 😉

      • Giscard Rasquin
        Apr 20, 2020


  • Products Explorer
    May 24, 2020

    How many presets are there. Do you have any list of them?

    • Adam Szabo
      May 24, 2020

      There are 4 factory banks containing 128 presets each

  • Products Explorer
    May 24, 2020

    I found them + Daniel.

  • Products Explorer
    May 28, 2020

    I finally bought it. I found many good features here and I will make a video about this synth.

  • Dean Zone
    Jul 17, 2020

    Can I install this on my PC and Laptop without causing licensing issues?

    • Adam Szabo
      Jul 17, 2020

      Hi, yes sure as long as they are your computers!

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