StringLife

StringLife is a guitar and bass string restoration effect plugin. It processes real recorded guitar/bass audio and makes old, dead strings sound fresher and more alive — without adding string noise, reverb, or delay.

Formats

VST3, AU, Standalone (built with JUCE 8).

Building

cmake -B build
cmake --build build --config Release

Requires CMake 3.22+. JUCE is fetched automatically via FetchContent (tag 8.0.4) — no manual JUCE checkout needed.

On macOS the build targets arm64;x86_64 with a deployment target of macOS 12.0.

Convenience build script

./build.sh licensed
./build.sh local-dev

This produces flattened artefacts under:

• build/licensed/Standalone/StringLife.app
• build/licensed/VST3/StringLife.vst3
• build/licensed/AU/StringLife.component

or the same layout under build/local-dev/.

macOS installer package

For a normal macOS installer (next -> next -> finish), build a .pkg:

./package.sh licensed
./package.sh local-dev

This creates:

• build/licensed/StringLife-licensed.pkg
• build/local-dev/StringLife-local-dev.pkg

The installer places the plugin system-wide into:

• /Library/Audio/Plug-Ins/VST3/StringLife.vst3
• /Library/Audio/Plug-Ins/Components/StringLife.component
• /Applications/Moth Production/StringLife.app

Notes:

• the .pkg is currently unsigned
• for public release you should sign and notarize both the app/plugin bundles and the final installer package
• the installer is the right approach if you want AU, VST3 and the standalone app to land in the expected macOS locations automatically

Windows installer package

For Windows, the repo now includes an Inno Setup based installer flow.

If you want to generate or inspect the installer script from macOS, install PowerShell first:

brew install powershell
pwsh ./package-windows.ps1 licensed

This lets you run the packaging helper on macOS, but it does not replace a real Windows packaging/signing step. The final installer still needs Inno Setup and release signing on Windows.

If the script says Missing build artefact ... StringLife.exe, that usually just means you are running it on macOS without an actual Windows build output. That is expected. The helper packages Windows artefacts; it does not create them from the macOS build.

Expected Windows build artefacts:

• build/<profile>/Standalone/StringLife.exe
• build/<profile>/VST3/StringLife.vst3

Then on a Windows machine:

.\package-windows.ps1 licensed
.\package-windows.ps1 local-dev

This script:

• checks the expected build outputs
• generates an .iss installer script from packaging/windows/StringLife.iss.in
• invokes Inno Setup if ISCC.exe is installed

Default Inno Setup location:

• C:\Program Files (x86)\Inno Setup 6\ISCC.exe

Or override it with:

$env:INNO_SETUP_COMPILER = "C:\Path\To\ISCC.exe"
.\package-windows.ps1 licensed

The generated installer places:

• the standalone app into Program Files\Moth Production\StringLife
• the VST3 plugin into C:\Program Files\Common Files\VST3\StringLife.vst3

Notes:

• AU is macOS-only, so it is not part of the Windows installer
• pwsh can run the helper on macOS, but the actual installer compile step still depends on Windows + Inno Setup unless you provide a compatible ISCC.exe environment yourself
• for public release, sign both the binaries and the final installer .exe

Licensing config overrides

The licensed build embeds Assets/licensing_config.json by default. For local server testing, build-time values can override the embedded JSON without editing the asset file:

LICENSE_SERVER_BASE_URL=http://127.0.0.1:8787 \
LICENSE_PRODUCT_ID=stringlife \
./build.sh licensed

Supported build-time overrides:

• LICENSE_SERVER_BASE_URL
• LICENSE_PRODUCT_ID
• LICENSE_PUBLIC_KEY

Reusable licensing stack

The reusable licensing module and the central licensing server were moved into a separate repository:

• /Users/mothproduction/Documents/VSCode/Licensing-VST

That repo now contains:

• the reusable JUCE client module
• the FastAPI licensing server
• Docker deployment files
• integration prompts for adding the licensing flow to other apps/plugins

StringLife now acts as one concrete integration example of that shared licensing stack.

Parameters

• String Age — master macro (0 = Dead, 1 = Fresh) driving four advanced parameters shown on the knobs as Spark, Bite, Shimmer and Bloom (internally still Presence/Attack Restore/Harmonic Excite/Sustain Shape). Each advanced parameter tracks the macro via a signed offset (its value minus the macro's value, captured the moment you last touched it by hand) rather than a one-shot copy — moving the macro shifts every parameter by the same amount, preserving whatever manual differences you've dialled in, like a synth macro with relative/offset mapping. A parameter clamps at 0%/100% if the macro pushes it past its range, but resumes tracking as soon as the macro moves back.
• Instrument — Guitar or Bass, changes the frequency focus of the restoration DSP (exact bands below under UI Reference).
• Wet/Dry Mix — only active in NORMAL monitor mode.
• Monitor Mode — NORMAL (processed output) or DELTA (wet minus dry, +6dB makeup). A/B and Bypass are separate controls, not monitor modes — see UI Reference.

Signal chain

Input -> Transient Enhancer -> Harmonic Exciter -> Presence EQ -> Upward Expander -> Wet/Dry mix -> Output

All continuously variable amounts are smoothed (sample-rate aware, no allocation or locking on the audio thread), so host automation and fast knob moves - including DEAD↔FRESH macro sweeps, which fan out to the four advanced parameters - don't produce zipper noise: the three envelope/waveshaper stages smooth their amounts per-sample over ~20 ms, the wet/dry mix crossfades per-sample over ~30 ms, and the presence shelf ramps its gain over ~50 ms with allocation-free coefficient updates at block rate while the value is moving.

UI Reference

Top bar

• StringLife title — branding only, no function.
• Guitar / Bass — sets the Instrument parameter, which changes the frequency focus of every DSP stage below:

  	Guitar	Bass
  Enhancement focus	2 kHz – 12 kHz	800 Hz – 6 kHz
  Presence shelf	5 kHz, 0 to +6 dB	2.5 kHz, 0 to +5 dB
  Harmonic Exciter high-pass	2 kHz	800 Hz

Main macro

• DEAD ↔ FRESH slider (String Age, 0–1) — see Parameters above for the exact offset-tracking mechanism. Current value shown below as "NN% Fresh".

Advanced row

Each slider's value is shown below it as a percentage (0–100%).

• Spark (Presence) — high-shelf boost. See the Guitar/Bass table above for frequency and max gain; filter Q is fixed at 0.707 (no resonant peak).
• Bite (Attack Restore) — transient enhancer. Envelope follower with 0.5 ms attack / 20 ms release; rising transients are boosted by a gain multiply of up to amount × 8 on top of the signal.
  TODO: naive envelope-derivative detector, no lookahead — see TransientEnhancer.h.
• Shimmer (Harmonic Excite) — harmonic exciter. A one-pole high-pass copy of the signal (cutoff per the Guitar/Bass table above) is driven through a tanh soft-clipper — drive scales up to ×3 at full amount, calibrated for ~0.3% THD at amount = 1 — and mixed back in at up to 30% of the driven signal's level.
• Bloom (Sustain Shape) — gentle upward expander on the decaying tail. Threshold fixed at −30 dBFS; below threshold, the distance to the threshold is compressed by a ratio of up to 1.2:1, i.e. quiet tails are pulled up towards −30 dB instead of decaying naturally. Envelope: 5 ms attack / 50 ms release.
  TODO: simple peak envelope, not RMS — see UpwardExpander.h.

Monitor section

• NORMAL / DELTA — mutually exclusive monitor mode:
  • NORMAL: dry/wet blend controlled by the MIX knob.
  • DELTA: outputs (wet − dry) × 2 (+6 dB makeup gain) — isolates exactly what the plugin is adding; ignores the MIX knob.
• BYPASS — hard, host-recognized bypass (also exposed as the plugin's getBypassParameter(), so a host's own bypass button/automation works too). Fully skips all DSP — output is the unprocessed input — and disables every other control in this section, since nothing else has an effect while bypassed.
• A / B — quick-compare toggle between two independent, full settings snapshots, not a dry/bypass switch. Flipping it saves every "sound" parameter (String Age, Instrument, all four advanced parameters, and the MIX knob) into the side you're leaving, then recalls the other side's stored values — both sides start out identical, and diverge as you tweak each one. The button label shows which side ("A" or "B") is currently live.

MIX knob

• Wet/Dry Mix (0–100%) — only enabled in NORMAL monitor mode; dimmed (but still visible) otherwise since DELTA and BYPASS override it.

Meters

• IN / OUT — vertical peak-hold meters, −60 dB to 0 dB, refreshed at 30 Hz. The white line is the peak-hold indicator: holds for ~1 second, then decays at 0.5 dB per tick (~15 dB/sec) until a new higher peak arrives.

UI assets & fonts

The panel background, button on/off states, knob face texture and the DEAD↔FRESH slider thumb are real rendered images (Assets/*.png), embedded via juce_add_binary_data. The rotary knobs use the image only for the static metal face — ticks, glow arc and pointer are drawn in code so every value renders correctly, since only one fixed-rotation render of the knob exists (see the comment in StringLifeLookAndFeel::drawRotarySlider).

Typography is three embedded Google Fonts (OFL-licensed, see Assets/Fonts/OFL-*.txt), not system fonts, so it looks the same on every machine: Oxanium (title), Barlow Condensed (everything else), Rajdhani (numeric readouts) — see StringLifeFonts.h.

Status

DSP stages are currently placeholder-quality (see TODO comments in Source/) — interfaces are stable but the algorithms need tuning against real guitar/bass recordings.