Tonetta Blue

Tonetta Blue is a semi-modular 8-voices polyphonic synthesizer for VST3 (64-bit). The frontside spots two type of oscillators, each with 19 waveforms to choose from, analog style filters, curve and LFO modulation, waveshaper, and a convolution reverb. Turning the "magic" back-button, reveal a modular environment with internal and additional signal sources and destinations, signal splitter and mixer, step sequencer, S&H, and additional, modular effects. 

https://flandersh.weebly.com/vst.html

XSRDO Analogy Modular Synthersizer

XSRDO Patchwork Modular System is a true modular synthesizer. You can choose what modules you want, where to put them and how many of them you want. Each module is independent of any other and only becomes active when you start to patch them together in your own creative way.

Features:

36 Virtual racks.
More than 50 modules.
Insert any module into any rack.
Insert multiple modules.
Movable modules.
Use of 3rd party wavetables and samples.
Load & Save preset programs.
Very low CPU usage.

- Added new switch to ARP module to select from 16 preset rhythms
- Polyphonic Padwave module
- Padwave Driver Module for pitch envelope mod, filter envelope mod, pitch mod etc...
- Added Slow/Fast option to Random/Noise Generator Module
- Added Slow/Fast option to Random/Noise Generator Module

https://xsrdo.blogspot.com

FullBucketMusic ModulAir

ModulAir is a modular polyphonic software synthesizer for Microsoft Windows (VST) and Apple macOS (VST/AU) written in native C++ code for high performance and low CPU consumption.

ModulAir is a work in progress, currently in Beta, unfinished, as of now with only a bunch of quirky presets and a lousy documentation. I am not sure if it ever reaches the General Availability stage since I am constantly adding modules and stuff to it:-).


Fully modular architecture.
Up to 18 modules per patch.
39 module types available.
Polyphonic Voice and monophonic Master modules.
TUN/SCL micro-tuning file import.
Up to 64 voices polyphony.
MIDI Learn – all parameters can be controlled by MIDI CC.
Double precision audio processing.
Plug-in supports Windows and macOS (32-bit and 64-bit).

https://www.fullbucket.de/music/vst.html

Fathom Mono Modular Synthesizer

Seaweed Audio has announced the release of Fathom Mono, the freeware monophonic version of the Fathom Pro ($35) modular wavetable synthesizer in VST plugin format for Windows-based digital audio workstations.

Fathom Mono is identical to the full Fathom Pro version feature-wise, except for its limited polyphony and the lack of ability to save edited waveforms. Everything else, entire synthesis engine included, is exactly the same as in the full product.

At its core, Fathom is a fully modular virtual synthesizer which allows the user to connect any two components together. The patching possibilities are only limited by the synth’s twenty available signal flow slots and, of course, the processing power of your computer. To help with monitoring the performance while creating a patch, Fathom shows a real-time CPU load readout in the upper-right corner of the GUI. The components are shown in a large panel in the middle of the interface with a handy real-time waveform display in the background. The patching of virtual cables is quite elegant, with a simple drag and drop workflow which doesn’t result in confusion and unnecessary clutter. The visual representation of the signal flow is also pulled off quite well, with easily identifiable modules and connections.

A modular synth ain’t no fun if you don’t have any interesting components to patch together, though. Thankfully, there’s tons of cool stuff to play around with in Fathom, from its five powerful oscillators to 30 different filter models, unlimited modulation sources, and custom waveform import (in WAV format). The oscillator types on offer are alias-free analog and additive, impulse and frequency pulse oscillators, and most importantly, the wavetable and wave draw oscillators which open almost limitless sound design possibilities. The filters are no less impressive, covering a range of common variants, along with the Butterworth filter and various analog-modeled filter types.

https://www.fathomsynth.com/#fathom

VCV virtual modular

Rack

VCV Rack is the engine powering VCV modules. Add modules, connect cables, edit parameters, and save/load patches. Create generative patches with your mouse, perform with your MIDI keyboard controller, or connect it to your favorite DAW using the Rack Bridge VST/AU plugin (coming soon). In Rack, control voltages and audio signals are equivalent, so you can modulate parameters with sonic-range VCOs to create customizable FM synths or chaotic wave-shaping oscillators. If you already own a modular synthesizer, you can enhance your setup with an audio interface supporting CV signals (see [1] [2]) or a CV-MIDI-CV interface module with Rack's CV Interface (coming soon).

Includes the Fundamental plugin pack with 8 high quality analog-modeling sound generators, processors, and utilities.

Audible Instruments

Based on the Mutable Instruments Eurorack modules, Audible Instruments gives you a collection of complex sound generators, modulation sources, sound modifiers, and signal utilities. All modules which are based on real digital modules are ports of their original source code, so generated signals are faithful to the hardware.

E-Series

The E-Series plugin features a port of Synthesis Technology's E340 Cloud Generator, a VCO capable of fat, chaotic, and swarming sound with up to eight combined saw and sine oscillators detunable with a spread parameter and filtered noise.

https://vcvrack.com

Throb clock

A free plugin for all your clock needs

Throb is a free and open-source JUCE based plugin that generates clock/reset signals synchronised with the host tempo. It is currently available for Windows (VST2 and VST3, 32/64 bit) and OS X (VST2, VST3 and AU 32/64 bit).
The user interface is pretty simple: a knob to set the multiplier and three radio buttons to configure the clock resolution.
The multiplier is an automation parameter and therefore can be controlled using the respective host functionality. Both the multiplier and the resolution (ppqn) settings are serialized to the preset chunk.
You won't need a DC coupled audio interface, but please avoid sending the output of the plugin directly to your speakers/headphones.

https://github.com/shaduzlabs/throb/releases

XSRDO Patchwork Modular System

XSRDO Patchwork Modular System, a freeware VST instrument plug-in for Windows, has been updated to beta version v0.58.

XSRDO Patchwork Modular System is a true modular synthesizer. You can choose what modules you want, where to put them and how many of them you want. Each module is independent of any other and only becomes active when you start to patch them together in your own creative way.

Features:

• 16 virtual 'racks' (with more planned for the future).
• More than 30 virtual 'modules'.
• Insert any module into any rack (except System, Output and Effects [of which only one instance of each type is allowed]).
• Insert multiple modules.
• Movable modules (except effects).
• Use of 3rd party skins, waveforms, wavetables and samples.
• Three track analog style sequencer.
• Built in waveform & wavetable editor.

http://xsrdo.net16.net/

Trilobite - evolutionary modular synth

a soft synth which lets you use Darwinian Evolution to create new modular synthesis audio patches.
Trilobite 0.9.3 is the successor to Cambrian Suite 0.9.2, and this time the evolutionary progression has been profound. Version 0.9.3 represents a "Cambrian Explosion" insofar as it makes the immense and necessary step of combining all of Darwin Arts previous separate evolutionary audio tools into one, with many other new features besides.

http://www.darwinarts.com/8-2/products/

VSTForx

(not free... a 4 plugin demo avalaible)

VSTForx is a full-modular effect network creation tool which comes as a VST-plugin. With VSTForx you are able to load any number of VST-plugins and connect them anyway you want.
Additional modules allow you to manipulate such signal chains and offer a whole new way in mixing and producing.

http://www.vstforx.de/