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


  • Adam Szabo
    Dec 20, 2019

    Please send me more info if it was 32 or 64bit viper, which factory bank and which presets crashed

  • anzwer
    Dec 22, 2019

    Thanks for update and Soundbank 4 !!!

  • Paolo
    Dec 24, 2019

    Hi, is license transfer possible fo r viper?
    best regards!

    • Adam Szabo
      Dec 24, 2019

      Unfortunately the way the licenses work for the product, does not make it possible to transfer them.

  • mike
    Dec 24, 2019

    Hi adam,

    you mentioned you were willing to do a christmass sale, are you doing this?

  • Anton
    Dec 29, 2019

    I tried the 64 bit version of Viper Demo V1.0.5 and noticed that reverbs and delays are not faded out when changing presets. Does it have to be that way?

    • Adam Szabo
      Dec 30, 2019

      Its only happening in the demo version, the full version does not do that. Hopefully I will fix the demo in the next version.

  • Sergey
    Jan 16, 2020

    Hi Adam.
    Any chances for non FlowStone ported version? Like PHAZOR.
    I’m waiting so long for mac version…

    • Adam Szabo
      Jan 16, 2020

      No chance. Phazor was a small plugin that was easily ported by one person, Viper is a huge project it would take someone many months to port it.

  • Daniel Reid
    Jan 26, 2020

    If I were to purchase this can I use it on two systems or only just one? Trying to figure out if I’m buying it twice or not.

    • Adam Szabo
      Jan 26, 2020

      You can use it on multiple computers but they have to be yours.

  • JP
    Feb 23, 2020

    Hey do you have plans to implement a sysex -> fxb system patch?

    • Adam Szabo
      Feb 23, 2020

      I am not sure thats possible

  • Tarvo Usen
    Feb 26, 2020

    Hey! Can i use Viper licence in two different computers? I start duo project with my friend and we living far from each others, that means we have to work with our project in differemt studios(mine and his).

    • Adam Szabo
      Feb 26, 2020

      The license is only for one person unfortunately.

  • digitalself
    Mar 08, 2020

    on the subject of FlowStone adding the ability to make Mac plugins – is that likely to ever happen?

    • Adam Szabo
      Mar 08, 2020

      Probably not

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