Overbridge Scenes

Octatrack-style scenes. A/B crossfader. No DAW required.

Snapshot a handful of parameters, assign them to four scenes per pattern, and morph between them in real time — Digitakt, Syntakt, Analog Heat, Analog Rytm, and the rest of the Overbridge family. A tiny local VST3 host drives the plugin and serves the web UI from your Mac.

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Control surfaces

Surface	Open it	What it's for
Scenes & crossfader	/scenes.html	Build scenes, morph, MIDI clock slide
Remote crossfader	/remote.html	Crossfader only — great on a phone over Wi‑Fi
Classic control	/	Browse, search, and tweak all 2,700+ parameters

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Screenshots & demos

Scenes & crossfader

Pattern bar, A/B assignment, crossfader, clock slide, four scene slots, and the parameter picker — the main event.

2D quad crossfader

Switch to 4 scenes (grid) to assign a scene to each corner, then drag the pad to bilinearly morph between all four.

Classic parameter browser

Search, pin favourites, nudge anything. Handy when you don't know the exact parameter name yet.

Remote crossfader

Crossfader-only surface for phones and tablets on your LAN — follows the active pattern from the desktop UI.

To regenerate these clips locally (uses the in-process fake plugin — no hardware required; writes MP4 + GIF under docs/videos/):

cargo build --release
OB_FAKE_PLUGIN=1 ./target/release/ob-host --fake-plugin --port 7780 &
npm install && node scripts/record-demo-videos.mjs

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What you get

Scenes & morphing

• 4 scene snapshots per pattern — each scene holds only the parameters you pick, at the values you want. Just like an Octatrack scene.
• A/B crossfader — assign a scene to each side and drag to morph every mapped parameter live. Snap buttons too: ⟵ A · B ⟶.
• 2D quad crossfader — assign four scenes to the grid corners and drag the pad to morph bilinearly between them.
• Pattern baseline — Capture baseline stores a neutral “home” per pattern for empty crossfader sides. No capture yet? Empty sides follow the live value.
• Param Learn — hit Learn on a scene card, wiggle a knob, and the parameter that moved gets added (or updated).

Patterns & persistence

• Per-pattern scenes on disk — data/scenes/<plugin>/<pattern>.json via the host API. Browser localStorage is a fallback only.
• Pattern selection & PC follow — banks A–P, patterns 1–16, or enable Follow Program Change to switch when the Digitakt sends MIDI PC (pick the port in the header MIDI selector).

MIDI & motion

• Clock slide — sweep the crossfader over N bars (default 8) from MIDI clock, locked to transport Start and bar 1. Uses the header MIDI input.
• MIDI crossfader mapping — absolute fader (0–127) or relative encoder, via host or Web MIDI.
• Debug MIDI log — --debug or OB_DEBUG=1 for a per-message log in the scenes UI.

Remote & live sync

• Remote slider — /remote.html is crossfader-only for phones and tablets on your LAN. Open http://<your-mac>.local:7780/remote.html (set System Settings → General → Sharing → Local Hostname) or use the IP from startup logs. Follows the active pattern from the desktop UI; override with ?pattern=B05.
• Live, bidirectional — hardware moves show up in the UI; UI writes hit the device. Default control-only mode leaves device audio to the hardware (or your DAW) while the host handles parameters.

For builders

• Full HTTP / WebSocket / MIDI API — poll, set, batch morph, send MIDI, roll your own controller. Scene files at GET/PUT /api/scenes/{plugin}/{pattern}.

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What's in the box (and what isn't)

This repo is source code only — no proprietary Elektron binaries.

Component	Included?	How to get it
Overbridge Scenes host + web UI	✓	Clone & build
truce-rack-vst3	✓	Vendored (MIT / Apache-2.0)
Elektron Overbridge VST3 plugins	✗	Install Overbridge → ./scripts/copy-plugins.sh
Overbridge Engine	✗	Ships with Overbridge; setup.sh may copy a local ref into vendor/ (gitignored)

plugins/, vendor/Overbridge Engine.app, and data/scenes/ stay on your machine — all gitignored.

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Audio routing

ob-host is control-only. It never opens the Elektron as a CoreAudio device and never writes to the USB audio return — so analog Main Out stays on the hardware's own mix, and a DAW can use Overbridge USB audio in parallel.

  Web UI / HTTP / WebSocket / MIDI
              │
              ▼
         ob-host (VST3 host)
              │
              ▼
    Elektron Overbridge VST3 plugin  ──►  Overbridge Engine  ──USB──►  device
                                              (params / MIDI only)

  Device audio: analog Main Out ←── hardware mix (or your DAW's Overbridge I/O)

Parameters are delivered through the edit controller (same path as the plugin GUI), driven by the hidden editor + main run-loop pump. No process() call, no host audio thread.

More detail: docs/architecture.md · docs/designs/audio-routing-and-control-options.md

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Quick start

git clone https://github.com/MartinNeifert/overbridge-scenes.git
cd overbridge-scenes

./scripts/setup.sh              # copy VST3s + build
./scripts/start-engine.sh       # Overbridge Engine (USB mode)
RUST_LOG=info ./target/release/ob-host --plugin Digitakt

open http://127.0.0.1:7780/scenes.html

Startup also prints LAN URLs for the remote slider:

LAN remote crossfader: http://192.168.1.42:7780/remote.html
LAN remote crossfader: http://digitakt.local:7780/remote.html

Want the MIDI tap? Add --debug:

RUST_LOG=info ./target/release/ob-host --plugin Digitakt --debug

More run modes and architecture: docs/architecture.md.

Tests

No hardware or VST bundle required — run the full suite as part of normal development:

./scripts/test.sh

This runs Rust tests (parameter round-trips, MIDI mapping, scenes HTTP API, fake-plugin Overbridge contract) and Node unit tests for crossfader morph math in web/scenes-morph.mjs. Equivalent: cargo test -- --test-threads=1 plus npm test. Optional live HTTP smoke: ./scripts/test-params.sh --live.

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How to use it

Build a scene

1. Choose a scene under Add parameters to.
2. Search → ＋ to capture the current live value.
3. Or Learn on a scene card + move hardware — biggest wiggle wins.
4. Snapshot live refreshes every param already in the scene from the device. Row sliders edit the scene value only (not the crossfader morph). ✕ removes a param.
5. Recall slams the whole scene to the device, crossfader aside.

Morph

Pick Scene A and Scene B, drag the fader. Every param in the union morphs like this:

Situation	What happens
Locked in both scenes	A-value ↔ B-value
Locked in one scene only	That lock ↔ baseline
Side is — None —	Other scene ↔ baseline

Capture baseline for a fixed home on empty sides. Clock slide auto-sweeps over N bars when you hit Play — set Bars to your pattern length.

Deep dive: docs/designs/scenes-crossfader.md.

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Programmatic control

Same powers as the UI — HTTP, WebSocket, virtual MIDI port:

curl http://127.0.0.1:7780/api/parameters | jq '.[0:5]'
curl http://127.0.0.1:7780/api/scenes/Digitakt/A01

Full reference: docs/api-reference.md.

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Docs

Doc	Why read it
docs/architecture.md	Layers, CLI, project layout
docs/api-reference.md	HTTP / WS / MIDI API
docs/designs/	Design notes incl. scenes & crossfader
docs/machines/	Device quirks (e.g. Analog Heat MKII)
docs/active-issues/	Known rough edges

Index: docs/README.md.

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Requirements

• macOS (Apple Silicon or Intel)
• Elektron Overbridge (/Applications/Elektron/)
• Rust (brew install rust or rustup)
• Hardware in Overbridge USB mode — not MIDI-only

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License

MIT License. Not affiliated with Elektron.