Tenebrae

A liturgy of shadows — cascaded high-gain distortion for the heaviest rhythm tone.

Work in progress. Tenebrae is pre-1.0 and under active development. Binaries for macOS and Windows are available from the Releases page (currently unsigned — see the release notes); building from source works too. Expect breaking changes until v1.0.0 ships (see Roadmap).

What it is

Tenebrae is a high-gain rhythm-guitar distortion built on JUCE 8, aimed squarely at the core "chug" tone of modern metal: a tightening high-pass ahead of a cascade of three oversampled waveshaper stages, each progressively tighter and darker than the last, followed by a passive-style 3-band tone stack for shaping the result. It has no cabinet simulation of its own - pair it with a cab sim/IR loader for the final voicing.

Features

• Tight - high-pass pre-emphasis, 20 Hz - 300 Hz (default 90 Hz), removes low end before the gain cascade so palm mutes stay percussive instead of farting out
• Gain - 0 - 40 dB of pre-gain into the 3-stage waveshaper cascade
• Voicing - Tight / Loose switch between two complete cascade voicings (asymmetry + interstage filtering): Tight is the tighter, more modern-leaning default; Loose is a softer-driven, wider-band, more vintage-leaning alternative
• Bright - fixed pre-cascade high-shelf switch, modelled on a high-gain amp channel's bright switch/a brighter cabinet's presence peak
• 3-stage cascade - each stage is gain -> asymmetric tanh clip -> a fixed interstage high/low-pass pair; the three stages use progressively tighter, more asymmetric voicing so the cascade converges onto a focused chug band instead of an ever-fizzier mess. Runs inside 8x oversampling to keep aliasing from all three stages out of the audible band
• Bass / Mid / Treble - passive-style tone stack (low shelf @ 150 Hz / peak @ 650 Hz / high shelf @ 5 kHz), +/-15 dB per band
• Tone Voice - Flat / Scoop / Boost one-switch dB tilt added on top of the live Bass/Mid/Treble bands, for quickly auditioning a canned high-gain-rhythm tone shape
• Presence - post-cascade high-shelf @ 2.4 kHz, +/-12 dB, modelled on the reference high-gain amp class's power-amp Presence feedback control; a true passthrough at its 0 dB default
• Gate - conventional fixed attack/hold/release expander/gate, gates the fully-voiced wet signal after the cascade and tone stack; on by default, the single highest-impact addition for "tight chug" tone research surfaced was missing from v0.1
• Level - output trim, -24 dB to +24 dB
• Mix - dry/wet, with the dry path delay-compensated against the oversampling latency so Mix at 0% is a sample-accurate passthrough
• Preset system - factory bank of 8 starting points plus save/load/rename/delete/import/export of your own presets, with English/German (auto-detected) frame localisation
• Full state save/recall via AudioProcessorValueTreeState

See docs/manual.md for the full user manual, including a musical description of every parameter and usage tips.

Signal flow

Input --> Tight (HPF, 20-300 Hz) --> Bright (switch) --> Gain (0-40 dB) --> [8x oversampled]
              Cascade stage 1 -> Cascade stage 2 -> Cascade stage 3   (Voicing: Tight/Loose)
                                                              |
   Output <-- Mix <-- Level <-- Gate <-- Presence <-- Treble <-- Mid <-- Bass <--+  (tilted by Tone Voice)
     ^
     |
delay-compensated dry path

See docs/architecture.md for the full breakdown, including the per-stage cascade voicing (both Tight and Loose tables), oversampling/latency-compensation strategy, and parameter smoothing.

Roadmap

Milestone	Description	Status
M1	DSP completion - Voicing/Bright/Tone Voice, refined tone stack, broadened test coverage (sample-rate sweeps, bus configs, long-run stability)	Done
M2	Preset system + factory presets + research-derived deep-dive voicing pass (Presence, Gate, Treble corner)	Done
M3	Custom GUI + accessibility pass	Planned
M4	Release engineering - signing, notarization, installers, v1.0.0	Planned

Installation

No pre-built binaries are published yet (see the work-in-progress notice above). Once releases begin, installation will follow the standard plugin locations:

macOS

Format	Path
AU (Component)	~/Library/Audio/Plug-Ins/Components/
VST3	~/Library/Audio/Plug-Ins/VST3/

If Logic Pro doesn't pick up the plugin after installing, force a rescan by resetting the AU cache:

killall -9 AudioComponentRegistrar
auval -a

Windows

Format	Path
VST3	C:\Program Files\Common Files\VST3\

Building from source

Requires JUCE 8.0.14, C++20, and CMake ≥ 3.24. See docs/building.md for full prerequisites and step-by-step build/test commands for macOS and Windows.

cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=Release
cmake --build build
ctest --test-dir build --output-on-failure

License

Tenebrae is licensed under the GNU Affero General Public License v3.0 (AGPLv3).

This project uses JUCE 8, whose open-source tier is licensed under AGPLv3 (as of JUCE 8; JUCE 7 and earlier used GPLv3), which is why this project is AGPLv3 rather than GPLv3. See docs/adr/0002-agplv3-licensing.md for the full reasoning.

VST is a registered trademark of Steinberg Media Technologies GmbH.

Tenebrae is an independent open-source project and is not affiliated with, endorsed by, or sponsored by any plugin manufacturer.