VoxSplit
Offline lead/backing vocal separation for macOS, as an FL Studio-compatible
VST3/AU plugin, a native SwiftUI app and a command-line tool. All three
are thin frontends over one Rust engine that runs ONNX models on the Apple Neural
Engine/GPU via CoreML. Nothing leaves your machine, and end users install nothing
else: no Python, no runtimes.
Download: https://voxsplit.jeffrey.build (Apple silicon, macOS 14+), or from Terminal:
curl -fsSL https://voxsplit.jeffrey.build/install.sh | bash # app + plugins + voxsplit command
curl -fsSL https://voxsplit.jeffrey.build/install.sh | bash -s -- --cli # only the command, no password
song.wav ─► Kim Vocal 2 ─► vocals ─► karaoke model ─► lead_vocals.wav + backing_vocals.wav
Best: BS-RoFormer Karaoke (frazer & becruily)
Fast: UVR-MDX-NET Karaoke 2, 3 refinement passes
| Quality | Model | 3:10 song on an M2 Max |
|---|
| Best (default) | BS-RoFormer karaoke, Core ML GPU | ~2 min (first run ever: about +1 min to compile) |
| Fast | MDX-Net karaoke, 3 passes | ~1 min |
| Vocal Remover | Kim Vocal 2 | ~15 s |
Two tools, in both the plugin and the app:
- Lead & Backing: the pipeline above. Vocal passes (0–5) sets how many times
Kim Vocal 2 runs (0 = the file is already vocals); Refinement passes (1–5) sets
how many times the lead/backing model runs.
- Vocal Remover:
vocals.wav + instrumental.wav from the vocal stage alone.
Both UIs show the expected time as soon as you choose a song, and a countdown
while it runs. Estimates learn from each run on your Mac.
Layout
engine/ Rust CLI (voxsplit / voxsplit-engine): decode → STFT → ONNX Runtime → overlap-add → WAV
plugin/ JUCE 9 plugin (VST3, AU, Standalone): drop zone, Separate, preview, drag-out
macos/ SwiftUI app (SwiftPM): the same flow; VoxSplitKit holds the async Process() runner
models/ ONNX weights (downloaded, gitignored) + committed sidecar JSON hyperparameters
installer/ .pkg pieces: distribution.xml, welcome/conclusion pages, postinstall
site/ voxsplit.jeffrey.build: Cloudflare Worker + static page + install.sh; installers in R2
assets/ the VoxSplit mark (icon.svg → macos/AppIcon.icns via scripts/make-icon.sh)
scripts/ fetch-models, build-engine, build-plugin, build-app, build-pkg, release, embed, sign, test-all
docs/ architecture, bundle layout, engine protocol, measured performance
Build (Apple Silicon, macOS 14+)
Requirements: Xcode command-line tools, CMake ≥ 3.25, rustup. The Rust 1.92
toolchain is pinned in engine/rust-toolchain.toml and installs automatically;
JUCE 9.0.4 is fetched by CMake.
scripts/fetch-models.sh # MDX weights (~120 MB, SHA-256 verified); exports the RoFormer
# via scripts/export-roformer.sh (needs uv; ~1 GB of PyTorch, once)
scripts/build-engine.sh # → engine/target/release/voxsplit-engine
scripts/build-plugin.sh # → dist/VoxSplit.{vst3,component}, installed to ~/Library/Audio/Plug-Ins
# (--no-install to skip; quit your DAW first if it has VoxSplit loaded)
scripts/build-app.sh # → dist/VoxSplit.app
scripts/test-all.sh # engine unit + CLI tests, headless plugin tests, Swift Testing suite
Bundles are assembled and ad-hoc signed in ~/Library/Caches/VoxSplit/stage
and copied to dist/. Building them outside the checkout is deliberate. If the
repo lives in an iCloud-synced folder (like ~/Desktop), macOS stamps Finder
metadata onto new bundle folders, and codesign refuses those. Run
codesign --verify on the staged or installed copies, not on dist/. For
distribution, set VOXSPLIT_SIGN_IDENTITY to a Developer ID and notarize.
Release (maintainers):
scripts/build-pkg.sh # → dist/VoxSplit-<version>.pkg: app + VST3 + AU + `voxsplit`, sharing one
# engine + models in /Library/Application Support/VoxSplit
scripts/release.sh # build-pkg, then upload to R2, update site/release.json, deploy the site,
# and check the live download (needs `wrangler login`)
Use the engine directly from the checkout:
engine/target/release/voxsplit-engine probe
engine/target/release/voxsplit-engine separate "$HOME/Music/song.wav" --keep-instrumental
cd engine && cargo run --release --example stem_check -- null "$HOME/Music/song.wav" "$HOME/Music/VoxSplit/song"
Using it
FL Studio: rescan plugins, then put VoxSplit on a mixer insert.
- Drop a song onto the plugin (or click to browse) and press Separate (or Return).
- When it's done, press ▶ above the stems to hear them all together; each stem's
speaker button mutes it. The preview replaces that insert's input while it
plays, so you hear it where you're working. Space plays and pauses.
- Drag a stem row onto the playlist, or press Reveal.
The run keeps going if you close the plugin window, and the result is saved
with the project.
App: the same flow in VoxSplit.app. You can also drop songs on its Dock
icon or use Open With. Stems are written to ~/Music/VoxSplit/<song>/.
Terminal: readable progress in a terminal, JSON Lines when piped (--format json forces it).
voxsplit separate song.mp3 # lead + backing → ~/Music/VoxSplit/song
voxsplit separate song.mp3 --quality fast --passes 3 --reveal
voxsplit separate song.mp3 --tool vocal-remover # vocals + instrumental
voxsplit play ~/Music/VoxSplit/song --mute backing # hear the stems together
voxsplit estimate song.mp3
See docs/ for the architecture, bundle layout, engine protocol and measured performance.
