Subtractive Synths

Podolskiu-he
Efficient single-oscillator virtual analog synth. Supports microtuning.
OB-XddiscoDSP
Virtual analog synth based on the Oberheim OB-X. Supports microtuning. Open source.
TAL-NoiseMakerTAL Software
Straightforward virtual analog synth with low CPU usage.
TyrellN6u-he
Compact virtual analog synth inspired in part by the Roland Juno-60.
VitalVital Audio
Spectral warping wavetable synth. Supports microtuning. Requires registration.
WhispAir Full Bucket Music
3-oscillator wavetable synth. Supports microtuning.
HelmMatt Tytel
Subtractive synth with an emphasis on flexible modulation. Open source.

Hybrid & Modular Synths

Surge XT Surge Synth Team
Hybrid synth capable of wavetable, subtractive, and FM synthesis. Supports microtuning. Open source.
CardinalDISTRHO
Unofficial plugin version of VCV Rack. Open source.
Odin 2TheWaveWarden
Semi-modular virtual analog synth. Supports microtuning. Open source.
Zebralette u-he
One-oscillator spectral synth. Must install Zebra2 demo.
Crystal Green Oak Software
Semi-modular synth featuring both subtractive synthesis and FM synthesis. No VST3 version.
ModulAir Full Bucket Music
Modular synth with over 50 modules. Supports microtuning.

FM Synths

DexedDigital Suburban
FM synth based on the Yamaha DX7. Supports microtuning. Open source.
OctaSineJoakim Frostegård
Simple but flexible 4-operator FM synth. No VST3 or AU version. Open source.
ADLplug/OPNplug Jean Pierre Cimalando
Pair of FM synths emulating AdLib (ADLplug) and Sega Genesis/Mega Drive (OPNplug) sound chips. Open source.

Chiptune Synths

Synth emulating the SID chip of the Commodore 64. Open source.
NES RP2A03SocaLabs
Synth emulating the RP2A03 chip of the Nintendo Entertainment System. Open source.
Gameboy PAPUSocaLabs
Synth emulating the PAPU chip of the Nintendo Game Boy. Open source.
Synth emulating the SN76489 chip of the Sega Master System, ColecoVision, and others. Open source.

Vocal Synths

Alter/Ego Plogue
Real-time singing synth with several free voices available.
Voc SocaLabs
Vocal synth based on the glottis and shape of the vocal tract. Open source.

Other Synths

Chow KickChowdhury DSP
Kick drum synth based on a physical model of the TR-808 bass circuit. Supports microtuning. Open source.
Unique synth based on comb filters. Supports microtuning.

Samplers

sfizzSFZTools
Sample player based around the popular SFZ file format. Supports microtuning. Open source.
sforzando Plogue
Highly SFZ 2.0 compliant sample player. Can also load .sf2 SoundFonts. Supports microtuning.
TX16WxCWITEC
Powerful sampler with support for SFZ, SoundFonts, EXS, and other formats.

Reverb

Dragonfly ReverbMichael Willis
Bundle of four different reverbs based on the Freeverb3 project. No AU version. Open source.
Massive reverb and delay effect.
TAL-Reverb-4TAL Software
Vintage reverb.
Reverb with a "classic" stereo reverb algorithm.
Mverb2020 SocaLabs
Update of Martin Eastwood's Mverb for modern systems. Open source.
OrilRiver Denis Tihanov
High quality algorithmic reverb. No longer updated.

Delay

Chow Matrix Chowdhury DSP
Delay using an infinitely growable tree of delay lines, with extra features such as pitch-shifting and distortion. Open source.
Multitap delay with pitch-shifting. Open source.
Valhalla Freq EchoValhalla DSP
Analog echo with Bode-style frequency shifter.
Tempo Delay Voxengo
Versatile tempo-synced stereo delay.

Modulation

Chow Phaser Chowdhury DSP
Phaser originally inspired by the Shulte Compact Phasing 'A'. Open source.
TAL-Chorus-LXTAL Software
Chorus inspired by the Roland Juno-60.
Very flexible flanger.
Emergence Daniel Gergely
Real-time granulator with up to 600 grains and 4 independent grain generation streams.
TAL-Vocoder TAL Software
Vintage 11-band vocoder.

EQ

Luftikus lkjb
EQ based on the Mäag Audio EQ4. Open source.
PTEq-XIgnite Amps
Emulation of three famous vintage EQs.
TDR VOS SlickEQTokyo Dawn Records
3-band mixing/mastering EQ with four saturation models.
TDR NOVATokyo Dawn Records
Parallel dynamic EQ.
Marvel GEQ Voxengo
Linear-phase 16-band graphic EQ with support for up to 8 I/O channels.
QRange lkjb
12-band IIR linear phase EQ.

Compressors & Limiters

DC1A Klanghelm
Two-knob character compressor.
MJUC jr.Klanghelm
Variable-mu compressor.
TDR Molotok Tokyo Dawn Records
Character compressor.
TDR Kotelnikov Tokyo Dawn Records
Mastering compressor designed to sound as transparent as possible.
OTTXfer Records
Multiband "upward/downward" compressor.
LoudMaxThomas Mundt
Look-ahead brickwall maximizer with a clean transparent sound.

Distortion & Saturation

Temper Creative Intent
Distortion with variable saturation curve and resonant lowpass filter. Open source.
Chow Tape Model Chowdhury DSP
Physical model of a reel-to-reel tape machine. Open source.
BYODChowdhury DSP
Modular distortion effect with circuit models of several classic guitar pedals. Open source.
IVGI Klanghelm
Mixing desk saturation.
BPB SaturatorBedroom Producers Blog
Analog-style tube and tape saturation.
Sophisticated tube preamp emulation.
Tube Amp Voxengo
Single-tube microphone preamp saturation.

Guitar Amps & Cabinets

Swanky Amp Resonant DSP
Authentic tube amp emulation with optional cabinet sim. Open source.
BoogexVoxengo
Classic amp and cabinet sim with impulse response (IR) loader.
Cypress TT-15Black Rooster Audio
Circuit model of the Orange Tiny Terror amp head, with an optional 2x12 cabinet sim. Requires registration.
NadIRIgnite Amps
Zero-latency dual impulse response (IR) convolver. Requires registration.

Metering & Analysis

SPANVoxengo
FFT spectrum analyzer.
Wave Observer Press Play
Oscilloscope with two different observer modes.
dpMeter5 TBProAudio
Multichannel meter with a variety of loudness measurement options.

Utilities

MTS-ESP MiniODDSound
Loads .scl, .kbm or .tun files and retunes all connected MTS-ESP client plugins for DAW-global microtuning.
Tuning Workbench SynthSurge Synth Team
Tool for experimenting with microtunings in real time. Open source.

MIDI

BlueARP OMG Instruments
Programmable pattern arpeggiator / step sequencer.
StochasSurge Synth Team
Advanced probabilistic polyrhythmic sequencer. Open source.
hypercyclic mucoder
LFO-driven, MIDI-mangling arpeggiator. No VST3 version.
tonespace mucoder
Chord generator and visualizer. No VST3 version.