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


  • 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 😀

  • Low Jin Kheng
    Oct 25, 2018

    Hi, I was going to purchase the viper but I noticed that I was charged the full amount of 89 euros even though I am not residing in the EU. Is there a VAT refund for those outside the EU?

    • Adam Szabo
      Oct 25, 2018

      Hi, there is no VAT, its 89€ for everybody. For europeans I pay their VAT from my own money so thats its fair for everyone.

  • Tim
    Oct 28, 2018

    Been a month since I’ve purchased this product and really happy with it! Certainly recommended! Are there any plans for future presets? I’m especially looking forward to more ambient driven ones like PD Ambient Pad. 🙂

    • Adam Szabo
      Oct 28, 2018

      Yes, many soundbanks are planned!

      • Ronald
        Oct 28, 2018

        Great news!
        I would also like more ambient and
        cinematic style sounds.

      • bLiNd
        Oct 28, 2018

        excellent news. I may make some myself since I am so familiar with the virus Ti. Right at home in your amazing plugin, thank you so much for making it!

  • OwnTrip
    Oct 29, 2018

    the frequency shifter is the same effect or similar of the virus ti2?

    • Adam Szabo
      Oct 29, 2018

      Its pretty much the same

  • Benjamin
    Nov 05, 2018

    Is there any estimate for when the resizeable GUI will launch? 🙂

    • Adam Szabo
      Nov 05, 2018

      Hopefully by the end of November

  • Chris
    Nov 06, 2018

    Hello , after using almost every vst this one looks very interesting to me and sounds really good of what I’ve seen in the demos and versus on YouTube, even better than sylenth ! And of course it looks beautiful, I wanna ask the one’s who buy it will have free lifetime updates ? Thanks

    • Adam Szabo
      Nov 06, 2018

      Hi, thanks, Im glad you like Viper! Yes, all updates will be free forever!

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