Curvessor 2

iPlug2 port in progress. A re-port of Curvessor onto the iPlug2 framework — with a modernized GUI (GPU-accelerated via NanoVG / Metal) and CLAP support alongside AU + VST3 — lives on the iplug2-port branch. See that branch's README for build instructions specific to the iPlug2 build. This master branch hosts the shipping JUCE-based version described below.

Curvessor is an audio plug-in that implements a dynamic range processor in which the response curve of each channel is an automatable spline.

Curvessor can be used as a classic compressor/expander, enjoying the freedom and precision that comes with spline editing.

But more specifically, as it allows the authoring of response curves that are not increasing, Curvessor can be used for creative dynamic range processing in sound design.

Features

• The response curves are smoothly automatable splines.
• Optional Mid/Side Stereo processing.
• Forward, Feedback and Sidechain topologies.
• The amount of feedback can be smoothly changed, going from pure forward topology to pure feedback topology and everything in between. (NEW in version 2)
• Optional RMS and high-pass filtering on the level detector. (NEW in version 2)
• All parameters, and all splines, can have different values on the Left channel and on the Right channel - or on the Mid channel and on the Side channel, when in Mid/Side Stereo Mode.
• Dry-Wet.
• Up to 32x Oversampling with either Minimum Phase or Linear Phase Antialiasing.
• VU meter showing the difference between the input level and the output level.
• Customizable smoothing time, used to avoid zips when automating the knots of the splines, the stereo link percentage, the wet amount, or the input and output gains.

Download

Pre-built binaries:

• macOS (universal — Apple Silicon + Intel): see the Releases page. Each macOS zip contains the AU + VST3 bundles, the legal/ folder, and a README.txt with install instructions (including the xattr -dr com.apple.quarantine step needed for unsigned OSS plug-ins).
• Windows / Linux: https://www.unevens.net/curvessor.html

Build from source

Clone recursively:

git clone --recursive https://github.com/unevens/Curvessor

Curvessor uses the JUCE C++ framework, referenced as a sibling checkout at ../JUCE. Clone JUCE 8 next to this repo before building.

The authoritative build is CMake (CMakeLists.txt at the repo root). The old Projucer .jucer file has been removed — see git history if you need it.

macOS

Apple's bundled Clang (Xcode 17, Command Line Tools 21) and any upstream Clang older than 22 hit a NEON-intrinsic codegen bug in Source/CurvessorDsp.cpp. The fix shipped in upstream LLVM 22, so build with Homebrew Clang ≥ 22:

brew install llvm

cmake -S . -B build \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_C_COMPILER=/opt/homebrew/opt/llvm/bin/clang \
  -DCMAKE_CXX_COMPILER=/opt/homebrew/opt/llvm/bin/clang++

cmake --build build -j8

CMakeLists.txt enforces this — configuring with Apple Clang or any clang older than 22 fails immediately with a message pointing at the right compiler. It also auto-derives llvm-ar / llvm-ranlib from the chosen compiler's toolchain dir.

This produces Standalone, AU, and VST3 in build/Curvessor_artefacts/Release/. The plug-ins are also copied to your user plug-in folders for an immediate DAW reload:

• ~/Library/Audio/Plug-Ins/Components/Curvessor 2.1.component
• ~/Library/Audio/Plug-Ins/VST3/Curvessor 2.1.vst3

Build options

Option	Default	Description
UNIVERSAL	ON	Build a universal arm64+x86_64 binary so a single zip serves both Apple Silicon and Intel users. Disable with -DUNIVERSAL=OFF for ~2x faster single-arch dev iteration.
INSTALL_TO_USER_PLUGINS	ON	Copy AU/VST3 to ~/Library/Audio/Plug-Ins/* after build. Disable with -DINSTALL_TO_USER_PLUGINS=OFF for CI builds or when you don't want the build to touch your live plug-in folder.

Release zips

cmake --build build --target package-zip produces both a staging folder and a ready-to-upload zip:

build/release-zip/
├── Curvessor2.1_mac/
│   ├── Curvessor 2.1.component
│   ├── Curvessor 2.1.vst3
│   ├── legal/
│   └── README.txt
└── Curvessor2.1_mac.zip

The platform suffix becomes _win / _linux when built on those hosts.

Windows

The CMake build is cross-platform via JUCE's juce_add_plugin. Windows is the next platform to be re-validated since the migration off Projucer. Adapt the cmake invocations above for MSVC, build, and please report any breakage.

Linux

The Linux build worked under the old Projucer setup but is not actively tested right now. The CMake setup should be cross-platform via juce_add_plugin, but expect to fix things if you build there. PRs welcome.

Submodules, libraries, credits

• oversimple wraps two resampling libraries:
  • HIIR by Laurent de Soras — a 2x Upsampler/Downsampler with two-path polyphase IIR anti-aliasing filtering.
  • r8brain-free-src by Aleksey Vaneev — a high-quality pro audio sample rate converter / resampler C++ library.
• audio-dsp, my toolbox for audio DSP and SIMD instructions, built on Agner Fog's vectorclass.
• gamma-env — DSP S-curve envelope signal generator by Aleksey Vaneev. Curvessor uses a SIMD-optimized version of gammaenv I wrote specifically for it; see audio-dsp/adsp/GammaEnv.hpp and audio-dsp/adsp/GammaEnvMacro.hpp.
• juicy, my JUCE-side UI/glue components (spline editor, attached controls, oversampling attachments).

License

Curvessor is released under the GNU GPLv3 license. Full license text and third-party notices are in the legal/ folder.

VST is a trademark of Steinberg Media Technologies GmbH, registered in Europe and other countries.

Version 1

For version 1, see the branch version-1.