This list is the result of years of demoing many plug-ins and considering which ones I feel like are the most worthwhile learning how to use. It's easy to get lost in the sea of plug-ins out there, so I hope this list helps you find the ones that are worth your time.
For those new to sound design, I would recommend starting out with the free plug-ins on here and then if you feel like you are not able to get the results you want or are looking for a better workflow, check out the paid plug-ins. I'm hoping that this guide can help save you time and money by pointing you in the right direction.
One limitation I gave myself was that I wanted to choose plug-ins with enough versatility that they could cover almost all the things you would need for each category. There are of course many plug-ins that are better at one thing than another, but I tried to choose ones that could cover a lot of ground. I think it's valuable to limit yourself a bit and get more familiar with the tools you have before buying more.
There is of course quite a bit of personal bias in this list, and I'm sure there are many plug-ins that I have not tried that are great.
Note: I've provided links for convenience. I have no affiliation with any of the companies listed below and I'm not getting paid to promote them.
- Nick von Kaenel
Analyzer
Free · Voxengo SPAN - A versatile spectrum analyzer.
Paid · Izotope Insight 2 - Comprehensive metering and audio analysis.
Bass
Free · Boz Bark of Dog 2 - Simple and effective bass resonance filter.
Paid · LeapWing RootOne - Advanced subharmonic generator for powerful low-end.
Chorus
Free · Kilohearts Chorus - A simple yet flexible chorus effect.
Paid · Melda MChorusMB - Multi-band chorus with advanced modulation options.
Compressor
Free · ReaComp - A solid, no-frills compressor included in REAPER.
Paid · Fabfilter Pro-C - A highly versatile and transparent compressor.
Compressor (Multi-Band)
Free · ReaXComp - Multi-band compression included in REAPER.
Paid · FabFilter Pro-MB - Flexible and transparent multi-band dynamics.
Delay
Free · Integraudio Sixth Sample Deelay - A versatile delay plug-in with a unique twist.
Paid · FabFilter Timeless 3 - High-quality tape delay with extensive modulation options.
Delay (Granular)
Free · UrsaDSP Lagrange - Creative granular delay for unique textures.
Paid · Unfiltered Audio Silo - Granular delay and reverb for transforming sounds.
Distance
Free · TDR Proximity - Simulate distance effects with precision.
Paid · Sound Particles Air - Realistic distance and air absorption simulation.
Doppler
Free · Aegean Music Doppler Dome - Doppler effect plug-in for realistic motion.
Paid · Tonsturm DopplerPro - High-end Doppler effect and spatialization tool.
EQ
Free · ReaEQ - Fully parametric EQ included in REAPER.
Paid · FabFilter Pro-Q 3 - Industry-standard EQ with dynamic processing.
Filter
Free · Tal-Filter (original version) - Simple and effective filter plug-in.
Paid · UVI Shade - Advanced filter and modulation effects.
Flanger
Free · Kilohearts Flanger - Simple yet versatile flanger effect.
Paid · Melda MFlangerMB - Multi-band flanger with extensive controls.
Frequency Shifter
Free · Melda MFreqShifter - High-quality frequency shifting plug-in.
Paid · Zynaptiq WORMHOLE - Frequency shifting and cross-synthesis effects for otherworldly sounds.
Granular Effect
Free · Daniel Gergely's Emergence - Real-time granular synthesis tool.
Paid · Melda MGranularMB - Multi-band granular synthesis plug-in.
High-End Enhancement
Free · Slate Fresh Air - Easy-to-use high-end enhancer.
Paid · Soundtoys Sie-Q - EQ plug-in with a unique smooth high-end boost.
Limiter
Free · ReaLimit - A reliable limiter included in REAPER.
Paid · FabFilter Pro-L 2 - Transparent and flexible brickwall limiter.
Memes
Free · Xfer OTT - Should be on every track.
Paid · Dada Life Sausage Fattener - Sosig.
Noise Removal (SFX)
Free · Bertom Denoiser - Simple noise reduction plug-in.
Paid · Sonnox Oxford DeNoiser - Professional noise reduction for sound effects.
Noise Removal (Voice)
Free · Bertom Denoiser - Simple noise reduction plug-in.
Paid · dxRevive Pro - Advanced AI-based noise reduction for dialogue and voice.
Pitch
Free · ReaPitch - Pitch shifting and correction in REAPER.
Paid · Polyverse Manipulator - Advanced pitch shifting and sound manipulation.
Phaser
Free · Melda Mphaser - Versatile phaser plug-in.
Paid · Soundtoys PhaseMistress - Vintage-inspired phaser with rich modulation options.
Phase Dispersion
Free · enummusic AllPassPhase - Simple phase dispersion plug-in.
Paid · Kilohearts Disperser - Unique phase rotation effect for enhancing transients.
Reverb
Free · Valhalla Supermassive - Epic reverb and delay effects.
Paid · AudioEase Altiverb 7 - Industry-leading convolution reverb.
Ring Modulation
Free · Melda MRingModulator - Flexible ring modulation effect.
Paid · Native Instruments Freak - Experimental modulation and ring modulation plug-in.
Saturation
Free · MSaturator - High-quality saturation effect.
Paid · FabFilter Saturn 2 - Versatile multiband saturation and distortion.
Speaker Effect
Free · ViatorDSP TeleVox - Emulate various speaker effects.
Paid · McDsp Futzbox - Customizable speaker and phone effects.
Spectral Compression
Free · ReaFir - Spectral processing tool included in REAPER.
Paid · MSpectralDynamics - Advanced spectral dynamics processor.
Stereo Imaging
Free · Izotope Ozone Imager - Free stereo widening tool.
Paid · Boom ReCenter - Professional stereo imaging correction.
Synth
Free · Vital - Powerful and fully featured wavetable synthesizer.
Paid · Xfer Serum - Highly popular and flexible wavetable synthesizer.
Tonal/Noise Separation
Free · Melda MRatioMB - Multiband crossover and separation tool.
Paid · Izotope Deconstruct - Deconstruct audio into tonal, noise, and transient components.
Transient
Free · Flux BitterSweet - Simple transient shaper.
Paid · Newfangled Punctuate - Advanced transient shaping tool.
Tremolo
Free · Melda MTremolo - Basic tremolo effect with flexibility.
Paid · Melda MTremoloMB - Multi-band tremolo with extensive options.
Other
Free · Waves Studio Rack - Customizable plug-in chain for mixing and mastering.
Paid · Zynaptiq UNVEIL - Advanced de-reverberation plug-in.
Paid · Zynaptiq UNFILTER - Adaptive tonal contour linearization plug-in.
Paid · Izotope RX Advanced - Industry-standard audio repair suite.
Paid · Izotope Neutron Advanced - Advanced mixing and analysis tool.
Paid · Voxengo TEOTE - Automatic spectral balancer. My personal favorite of the ones out there.
Paid · GRM Contrast - Sound shaping and morphing tool.
Paid · Eventide SplitEQ - Advanced equalizer with transient and tonal split.
Paid · Tonsturm SpinTracer - Creative doppler effect. Super useful for adding movement.