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


  • Key
    Oct 10, 2019

    Hi Adam, i have tested the demo version and the synth sound awesome, you did a really great job. But i have noticed some latency when i put a sidechain fx (i’m on FL 20), it’s first time i see that on a synth vst plugin (usually it’s on some fx). I really want to buy the synth but for now with the latency problem, i can’t use it :-(( maybe it’s due to the demo version? thank you

    • Adam Szabo
      Oct 10, 2019

      I dont have any latency problems here. I would need to see a video of whats happening to figure out whats going on.

      • Key
        Oct 11, 2019

        Finally it was me^^ Kickstart make an awful sidechain. A real sidechain with a compressor sounds perfect, so i bought the plugin!

  • August
    Oct 19, 2019

    After latest Win10 update, when i try to drag and drop Viper Vst into studio one 4, nothing happens. Any ideas what could’ve happened?

    • Adam Szabo
      Oct 19, 2019

      Try to install the c++ 2013 redistributable package, it is required for the synth to run

      • August
        Oct 21, 2019

        It works! Thank you very much

  • Denis Baranov
    Oct 21, 2019

    really can’t wait mac os x version 🙂

  • LVL
    Nov 19, 2019

    Alright my good sir! Open the floodgates on the Sale so we can stop Resampling the synth already 😉

  • digital experience
    Nov 25, 2019

    black friday or cyber monday Adam?

    • Adam Szabo
      Nov 25, 2019

      I hope to do a Christmas discount

    • Erik
      Nov 28, 2019

      Sounds like no 🙁

  • Nico Østergaard
    Dec 16, 2019

    The 1.0.5 update is spot on! Using the matrix to speed up the LFO rate was just what I needed from this synth!

    Thank you <3

  • Madalin
    Dec 17, 2019

    Hi Adam, is there any AAX version of the plugin?

    • Adam Szabo
      Dec 17, 2019

      Unfortunately no, only vst

  • LMG
    Dec 17, 2019

    Loving the sound and I would love to buy this, but this is the only plugin on my machine that is causing massive jittery spikes on Bitwig 3, is there any sollution for this? I tried 32bit and 64bit versions.

    • Adam Szabo
      Dec 17, 2019

      Unfortunately its a bug in FlowStone (the software I use to create Viper) and I have to wait until they fix it.

      • LMG
        Dec 18, 2019

        Ok, thanks for the reply.

        I will buy this now and hope it will be fixed in the future! Do you know that are there any other DAWs that have this issue?

        • Adam Szabo
          Dec 18, 2019

          The problem is with Viper and not the DAW

  • James Rittenburg
    Dec 17, 2019

    this synth is impressive for being made in Flowstone

  • guy
    Dec 18, 2019

    How much licences can used?

    • Adam Szabo
      Dec 18, 2019

      You can use the license on several computers that you own

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