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
 ● Built in Preset browser
 ● Section locking
 ● Midi learn


Download demo version:
Demo restrictions: Preset saving is disabled. Noise 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


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  • david88m
    Oct 01, 2018

    Congratulations Adam, Viper is really good, it’s amazing to think that it was created with Flowstone.
    Thank you for your work.

  • Lorenzo
    Oct 06, 2018

    As I mentioned before, I find the maximum LFO rate very slow compared to other plugins. Is there a possibility that this will be changed in the future? See also the comment of Nico as a refferance

    • Adam Szabo
      Oct 06, 2018

      I am not sure, existing patches will sound different if I increase the LFO rate. I guess I can do it but people will have to adjust their old patches accordingly.

      • Lorenzo
        Oct 07, 2018

        Please, take it into consideration. As an example: the maximum LFO rate in Sylenth is 192.0 Hz. Nothing compared to the rate of 43.0 Hz in Viper.

        Actually for me this is the only reason I haven’t bought this plugin yet, since I often use the LFO as an extra detune layer. Fast LFO speed can give cool effects on certain sounds, especially in electronic dance music.

  • humphrey
    Oct 07, 2018


    Even though I respect the wish for increased LFO speed: please make this happen without attaching existing patches (f.e. by introducing a selector switch „low – high speed“ with default setting „low“ for existing patches).

    I‘m using Viper live and created quite some patches embedded in racks I don‘t want to recreate. For live use stability of the situation is quite important.

    Regards, humphrey

  • Daniel Hernandez
    Oct 14, 2018

    Adam, i want to buy Viper with 4 friends? Its ok? or max 2 people per lic.?

    • Adam Szabo
      Oct 14, 2018

      Its 1 person per license.

  • yvez
    Oct 15, 2018

    Hi1 I like this!
    Do you have any more presets available?
    Wouldve been nice to have 500+ presets 😀

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Oct 21, 2018

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