Audio plug-ins for macOS that are genuinely free. Not trials, not time-limited demos. Not cut-down versions of a paid tier. Every entry here is listed as free on AlternativeTo. They install as Audio Unit or VST/VST3 plug-ins in Logic Pro, Ableton Live, Reaper and GarageBand.
Instruments and samplers come first, then effects and processors. Several also run on Windows or Linux; each app page has the details.
Disclosure: I develop one of these plug-ins, StudioZIO Tempo Delay. The rest is other people's work, included because it is well known and actually free.
Magical 8bit Plug 2 is a VST plugin that synthesizes the sounds of 8-bit gaming consoles like the NES including modular pulse waves, pseudo-triangle waves, and 4-bit random and 1-bit pseudo-random noise.
The Decent Samples plugin is a FREE sample player plugin that allows you to play sample libraries in the DecentSampler format (files with extensions: dspreset and dslibrary).
Odin 2 is a versatile 24-voice polyphonic synthesizer that covers about every type of synthesis out there. Odin 2 is released as open-source software.
ZynAddSubFX is a fully featured open source software synthesizer capable of making a countless number of instruments, from some common heard from expensive hardware to interesting sounds that you'll boost to an amazing universe of sounds.
Dexed is an FM-type softsynth developed by Pascal Gauthier of Digital Suburban. It is an ideal application for importing, playing and editing/managing sysex patches from both the classic Yamaha DX7 synthesizer and the TX7.
Helm is a free, cross-platform, polyphonic synthesizer with a powerful modulation system. Helm runs on GNU/Linux, Mac, and Windows as a standalone program or LV2/VST/VST3/AU plugin.
Surge is an open source digital synthesizer originally written and sold as a commercial product by @kurasu (Claes Johanson) at Vember Audio. The synth uses subtractive hybrid synthesis and each patch contains two 'scenes' which are separate instances of the entire...
Vital is a spectral warping wavetable synthesizer with drag'n'drop modulation workflow and animated preview of the synth's inner workings where needed. Comes with many modulation sources (including audio-rate), MPE support and FX chain.
The IEM Plug-in Suite is a free and Open-Source audio plugin suite including Ambisonic plug-ins up to 7th order created by staff and students of the Institute of Electronic Music and Acoustics.
Rough Rider is a compressor effect available as VST and Audio Unit plugins for Windows or Mac an as an Inter-App Audio compatible effect for iOS devices.
Marvel GEQ is a free linear-phase 16-band graphic equalizer AudioUnit, AAX, and VST plugin with multi-channel operation support (supporting up to 8 input/output channels, audio host application-dependent) for professional music production applications.
NOVA is a parallel dynamic equalizer. Appearing in the familiar layout of a parametric equalizer, each band also includes a full featured dynamics section allowing the processor to cover an impressively wide range of applications.
The TAL-Reverb series are high quality, algorithmic reverb plugins for Windows and Mac available in VST and AU unit formats. They are highly regarded as some of the best on the free market.
A free tempo-synced stereo delay for macOS whose left and right delay lines run on fully independent buffers and note divisions.
