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


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  • BigBootyTrap 40_5
    Feb 22, 2018

    When will 64-bit come out? Like how long does it take to convert it to 64-bit and what do you use to convert it like you convert the phazor to 64-bit before it was 32-bit

    • Adam Szabo
      Feb 22, 2018

      Phazor was converted by someone else, I will use a new version of Flowstone. 64 bit will arrive in about a month

      • Dylan Loera
        Mar 08, 2018

        too stoked if that is true 😀 I have my money ready!!

  • humphrey
    Mar 04, 2018

    Hi Adam,

    first off: incredible work, Viper is awsome!! Terrific sound in combination with simple workflow make fast results. Even though I didn‘t purchase it as substitute for a Virus it also seems to be the best contender to it ;-).

    Atm I‘m eagerly waiting for the x64 release (and glad to her this will be also realised for JP6K btw – good decision).

    One small idea: as Viper can be a real cpu hog (and yes: I read the manual with the hints for decreasing cpu consumption) would it be possible to implement options for chosing different quality levels and / or multicore support to decrease cpu use as it is implemented in some of the u-he synths?

    Anyway: very happy with Viper, thanks and kind regards, humphrey

    • Adam Szabo
      Mar 04, 2018

      Thanks Im glad you like it! Unfortunately multicore is beyond my control and if I would add a quality control I would have to rewrite the whole synth as its not designed that way.

  • michael
    Mar 09, 2018

    Yes i would by it instantly as the MAc version will be released

    let the world know

  • paul
    Mar 15, 2018

    Hello Adam !
    64 bits version is coming? this is dams good
    any idea about a bundle (jp6k+viper) at a special price for this so anticipated upgrade?

    • Adam Szabo
      Mar 15, 2018

      64 version is weeks away! I dont know about a bundle yet I havent had time to think about it I am very busy with the 64 bit.

  • Andreas
    Mar 16, 2018

    Hi Adam,

    Wondeful sound. Bought instantly. Looking forward to the 64-Bits version but 32-Bits works without problems so no hurry 🙂

    Wondering if we would be able to load/convert Virus patches in future?



  • Craig
    Mar 25, 2018

    Where is the demo link for this? Thanks

    • Adam Szabo
      Mar 25, 2018

      Try the huge “download” button beside the “Download demo version:” text

      • Craig
        Mar 25, 2018

        Thanks, it wasn’t immediately obvious it was a button. It just looked the like it was stating it’s a Windows application.

  • Awesome! Cant wait to start!

  • JAMp
    Mar 31, 2018

    Any thoughts on putting this beauty synth on Splice for Rent-to-Own service? I think this synth will be as boom as Serum if it goes into that service, looking on how much people appreciate Virus as a versatile synth to have around.

  • fil
    Mar 31, 2018

    64bit version please, i don’t use any 32bit soft anymore in 2018.

  • bLiNd
    Mar 31, 2018

    No worries on 64 bit as I use jbridge for many other vsts, but WONDERFUL work. I lost my studio in a fire, including my virus snow and this Viper synth has made me content, thank you so much for making an awesome piece, using it in my new trance/psytrance albums now!

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