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There isn't a regular oscillator section exposed on this synth, only three main parameter knobs and the fundamental saw adjustment.

This is intentional and very ROMpler'y. But without being a rompler...

A synth made with FlowStone... is a simple experimental synth available in Windows VSTi format as free download for your enjoyment.

Note since i'm not much of an audio- or DSP-engineer and being rather experimental, it can exhibit sound issues depending on settings. Aliasing and such.

What is it then? can be considered a barebone 1 + 1 oscillator synth of sorts

Using mainly the just the saw waveform, hence the name saguaro. combines and mixes saw with sine, triangle, square and noise in selectable pre-wired Osc modules. No advanced analog emulation, no special unison or stereo FX, no delays nor built-in reverb. Just pure harsh digital mayhem. 

To understand the idea of the synth choose a default (blank) patch and try the different Osc modules. Tweaking P1, P2 and P3.
Adjusting these parameter knobs on an already made preset won't yield a satisfactory change since they are likely already modulated.

All donations are very much appreciated!

This synth was mostly made for fun and learning purposes. But if you enjoyed you are welcome

to show appreciation and support me as a creator by making a Paypal donation. 

Big thanks to MV
His contributions to the FlowStone community made this plugin possible.

MV deals in more advanced audio/image processing than any of the modules of his implemented in

MV's website can be found here

System requirements

Both standalone / vsti version:

  • Microsoft Windows 7, 8 or 10
  • 4-core CPU @ 3.0 Ghz or higher
    Recommended later gen i5/7 @ 3.5 Ghz or higher
    This plugin can be demanding of CPU. I recommend freezing tracks
  • Up to 1024 megabytes of free RAM (plugin itself)
  • Microsoft Visual C++ Redistributable Package for Visual Studio 2013
  • Sound device with low latency ASIO drivers

    You can emulate ASIO device by using ASIO4ALL driver
    which can be found here:

  • External MIDI-keyboard for Standalone version

Specific to vsti version:

  • DAW software that can host VST2/3 plugins (32 or 64-bit)
    - Compatibilty with any particular DAW is not guaranteed
    - Reaper usually works fairly well

Known issues (most releases)

  • Standalone .EXE version only: Holding down left mouse button and clicking right mouse button at the same time will freeze knobs.  If a knob is frozen the standalone version of the synth has to be restarted.

  • Both VSTi and Standalone version can sometimes be rendered silent. Usually solved by clicking "If synth has issues" button. Alternatively changing program preset or oscillator module.

  • You should always use an ASIO sound device. Playing the synth on a non ASIO sound device sounds awful and usually results in high latency. Please use an ASIO sound device.
    You can emulate ASIO device by using ASIO4ALL driver which can be found here:

    Note: that asio4all is a temporary solution and doesn't always work well, it has it's own issues


June 2024 update NEW

May 2024 update #3

  • export version 0.521

May 2024 update #1-2

  • export version 0.51-0.52

Upcoming Updates

  • Rand Detune additional options
  • 2 additional mini LFO's... maybe
  • Adjustments/changes regarding Aftertouch
  • More Osc Modules


These are possible updates if interest for the plugin

is great enough and it's CPU usage doesn't hit critical levels

even on fast systems

Future updates & ideas

  • More osc modules
  • Changes in GUI to improve Usability 
  • Fixes, optimizations and minor adjustments screenshot 1/11 screenshot 2/11 screenshot 3/11 screenshot 4/11 screenshot 5/11 screenshot 6/11 screenshot 7/11 screenshot 8/11 screenshot 9/11 screenshot 10/11 screenshot 11/11


Selected features

    • Polyphony: 1 up to 64 voices  (depending on CPU)
      - Voices adjustable all the way up to 512 for bounce
    • 2 Filters
      - Selectable LP/HP/BP/Peaking and different filter combos
      (most of them created or optimized and shared by MV) 
      - 3 filter routing modes: Parallel, Series 1 and Series 2
    • 5 simple ADSR/AHD envelopes: 1 amp, 2 filter + 2 modulation (flip +-) 
    • 2 non syncable LFOs with standard waveforms
      - Non syncable but can be triggered by automation/manually to hard sync
      - Uni/Bipolar Offset per individual destination
      - Odd/Even waveform flip by voice option
    • 3 custom assignable knob controllers
      - Select input from auxiliary knob, modwheel,
      aftertouch, pitchbend or midi-cc's
      - Controls any number of knobs at the same time
    • Rudimentary velocity modulation
    • Rudimentary velocity to envelope
    • Rudimentary pitch (tracking) modulation
    • Rudimentary pitch to panning option
    • Scalable GUI (freely resizable in VST3 64-bit version)
    • Pitch controls and other basic controls are there...

    • Distortion
      The FlowStone toolbox distortion was thrown in for good measure. It does have some aliasing. Use a good external distortion plugin for even better results.


    As the FlowStone export of the synth is free... Charging money for or bundling it with other software and selling it without permission is not permitted. Modifying or any part of it's code without permission from it's creator is also not allowed.


    Whats on your mind

    If you have any thoughts, ideas or suggestions surrounding this little VSTi / Standalone synth project. Let me know...

    There is no official support for the synth since it is both free and at the mercy of my ignorance and any behaviour inherent to FlowStone itself.

    But you are welcome to report any bugs or incompatibility issues with different DAWs and/or Windows versions.

    Not all messages are answered. But I read all and take any suggestions into consideration...


    Good to know...

    • Hold down SHIFT, ALT or CTRL-key on keyboard for fine, coarse or snap-to adjustment of knobs.
      LFO frequency is adjustable in steps around 0.001 Hz

    • Easily automate or control multiple knobs such as both filters cutoff at once using one knob. Without creating multiple automation tracks
      Example of using Assignable C1 for direct control over filter 1 & 2 cutoff's...

    • The more automation you do the more CPU is consumed. Especially automating interactively using's own GUI
    • Turn off scope visualization to save a bit of CPU or hide the plugin GUI using the DAW
    • If you experience silence, notes that get stuck, filters, lfo:s or envelopes acting up. Try pressing If synth has issues button or changing preset back and forth
    • DAW host usually saves values (preset/knobs) for VSTi with it's project. This is not the case with Standalone version
    • Loading banks takes a long time. Have patience. Do not close the VSTi / Standalone to early when saving banks and preset to file
    • Programs/presets and banks are in plain text format and can therefore be viewed with any text editor, like Notepad
      They do however contain <2000 parameters for each program/preset. Thats 99 x 2000 parameters in one bank