Kuma 508

beatassist.eu has released Kuma 508, a free FM synth plug-in for macOS and Windows that features 5 oscillators and a noise generator.

There are 5 FM algorithms and 3 Single Osc modes. Kuma 508 has the possibility to play among 22 extra waveforms per Oscillator. The plugin has 4 filters that can be connected as a modular synth VIA patch cables. There is also a basic but effective Reverb inside Kuma 508. 

https://www.beatassist.eu/kuma508.htm

Exakt Lite

Exakt Lite is an intuitive and user friendly FM synthesizer plugin. From the harsh digital and cold sounds known from the FM era to warm and organic sounds, Exakt Lite can create a wide range of sounds.
Exakt Lite has got 4 operators which can be arranged in the classic 8 FM algorithms with feedback on operator D. Each operator has got different waveforms such as the basic sine, saw, square and triangle. Additionally, the 8 classic waveforms from the Yamaha TX81Z are emulated.
Each operator has got a separate amplitude envelope generator supporting the classic 5 point TX envelopes. These envelopes have been modeled to mimic the TX characteristics.
The plugin UI has been created using vector graphics and supports blur free resizing.

• 4 aliasing free Operators with classic TX waveforms
• 12 voices
• Drag-and-drop envelopes
• 8 classic FM algorithms with feedback on operator D
• Resonant filter with 24db/oct lowpass, highpass and bandpass
• Visualization of the resulting waveform for immediate editing response
• LFO syncable to host

https://www.sonicbits.com/exakt-lite.html

Digital Systemic Emulations Syncla-X Synthesizer

Syncla-X is an emulation of the Synclavier FM unit and is available for PC & Mac.

The first free emulation of the Synclavier FM Unit... Extended.

4 Carriers, 4 Modulators

8 Harmonics generator

8 ADSR + 2 ADSR

Individual Pans

Velocity

Filter

Mono/Poly modes

2 LFOs

Flanger and bitdepth

https://sites.google.com/site/digitalsystemic/home/syncla-x?authuser=0

Dead Duck Free Instruments Bundle

The Dead Duck Free Instruments Bundle presents updated versions of four VST classics from mda:

• DJX10 subtractive synth. 
• DDX10 FM synth. 
• DPiano-A 'acoustic' piano. 
• DPiano-E 'electric' piano. 

http://deadducksoftware.blogspot.com.es

Erik Wollo VSTs

http://www.wollo.com/vst.htm

WOLLO DRONE




WOLLO FMERA




WOLLO BEAT




WOLLO SPACER

Krakli K200 FM Synthesizer

K200, a 4 operator FM synthesizer (with 52 algorithms!)
Krakli’s latest freeware instrument is a 4 operator FM synthesizer, packed in a slightly unusual looking but actually rather user friendly interface.
The included set of factory patches crafted by Armin Kujashi features some lovely sounding bells, pads, and most of the other classics you’d expect to hear in an FM synth. The real fun begins when you start tweaking those patches (or building your own from scratch).
Other notable features include a multi-mode filter (LPF, BPF and HPF) with a filter envelope, a master tune knob and octave switch, pitch bend amount knob, portamento, mono/poly switch and MIDI learn support. The synthesizer also includes two built-in effects: a simple reverb module and a nice sounding chorus.

http://bedroomproducersblog.com/2016/03/09/krakli-k200-fm-vst/

Oxe FM Synth

Oxe FM Synth is a freeware VST 2.4 instrument plugin for Windows.

Features:
Multitimbral (16 MIDI channels);
8 operators (6 oscillators, 1 noise generator/limiter, 1 filter), all with envelope;
1 LFO per channel;
frequency modulation half-matrix with self-modulation;
global reverb and delay;
great general performance in low resources systems;
a lot of good quality patches included (thanks to Annabelle, Summa and Teksonic);
external skin support (download lcd, snow, tx802 skins by Layzer andtotolitoto’s skin by David Frappaz).

http://www.oxesoft.com/

Dexed

This is the best Yamaha DX7 emulation in the freeware world.
The plugin is closely modeled on the architecture and sound characteristics of the legendary DX7. In fact, it is even capable of loading the original SysEx programs for the DX7, hundreds upon hundreds of which are freely available on the world wide web.
http://bedroomproducersblog.com/2014/06/15/digital-suburban-dexed/
https://github.com/asb2m10/dexed

T-Force Alpha Plus

Alpha Plus is a hybrid trance-gate synth.

It is the advanced version of the T-Force Alpha TS. It has all features of the Alpha TS with some more and some updated functions: new sythesis (Subtractive and additionally FM Synthesis), revised oscillators with some more functions and now with a separate noise oscillator, new Mod Envelopes and now with a new integrated Sidechain FX (e.g. for the typicyal sidechained pad sounds and/or pumping basses etc.).

http://www.vst4free.com/free_vst.php?id=1426

Mantra evo

Mantra Evo it´s a plugin that combines 2 synths with several effects.
It is based on an FM synth and a Phase Dist synth.
Both of these synths are gifted with a morphing system that will morph the basic waves into some more complex ones.
Each of these synths are also gifted with 5 envelopes (amp, pitch, filter, modulation and morphing).
The modulation of these synths is based on FM modulation system using kbd and depth.
On the filter envelope you can tweak just cutoff, resonance or both.
Each of these synths are gifted of an LFO with two targets, dedicated filter, free speed knob, sync option and waveform choice.
There is a Chorus for each synth too, making your sounds phater.
http://www.beatassist.eu/mantra-evo

Xen-Arts Xen-FMTS 2

Xen-Arts has released Xen-FMTS 2 – a free microtonal synthesizer for Windows.

Xen-FMTS 2 is a 4 Operator FM Synthesis VSTi with a specialized set of features for computer musicians interested in exploring the possibilities of making music with alternative intonation systems

It is a freeware 32-bit plugin instrument for Windows that includes 115 patches, 55 microtunings and 56 partials files.

http://www.xen-arts.com/2014/02/xen-arts-virtual-instrument.html

Solcito Música

Sintetizadores virtuales

Arido 1.0 is an additive synthesizer which includes a polyphonic driver to generate greater variety of timbres.
SuperSonico 2.0 is a virtual analog synthesizer with a small additive section. 
It has a single oscillator with a generator of harmonics. The Sub-Oscillator includes an option that generates a single low octave that is repeated along the keyboard.
...
SuperTron (Dance Filter), VintagerToy (Fx), EmulTuition (FM)...
http://solcitomusica.blogspot.com.ar/p/virtuales.html

Xen-Harmonics FMTS

Xenharmonic FMTS is a 4 Operator FM Synthesis VSTi with a specialized set of features for musicians interested in exploring the expressive possibilities of microtonal and xenharmonic music making.