Général Midi Boop

Turn a pile of DIY MIDI instruments into a real orchestra — from a Raspberry Pi, with no internet required.

Général Midi Boop is a complete MIDI orchestration system designed for beginners building DIY MIDI instruments. Plug in your home-made or off-the-shelf instruments, point a standard MIDI file at them, and the system automatically adapts the music to what each instrument can actually play — then conducts the whole ensemble in sync.

It is built to run standalone on a Raspberry Pi without any internet connection. Everything is driven from a modern, touch-friendly web interface you reach from a phone, tablet or laptop on the same network — or directly from the Pi's own WiFi hotspot.

Quick install (Raspberry Pi)

git clone https://github.com/glloq/General-Midi-Boop.git
cd General-Midi-Boop
chmod +x scripts/Install.sh
./scripts/Install.sh

Then open the interface at http://<Raspberry-Pi-IP>:8080.

The installer sets up Node.js, system dependencies, auto-start on boot and (optionally) Bluetooth — see docs/INSTALLATION.md for detailed configuration and other platforms.

Highlights

• Connect instruments over USB, Bluetooth LE, network (RTP-MIDI, experimental) or physical MIDI IN/OUT on the Raspberry Pi GPIO.
• Conduct up to 16 instruments at once, with per-device latency compensation and an optional MIDI clock.
• Automatic routing of MIDI channels to the best-suited connected instrument.
• Automatic adaptation of any MIDI file to each instrument's note range and polyphony.
• Play live from a virtual keyboard, and build loops and arrangements from the Loop manager.
• Preview any loop or MIDI file with the original sound or the instrument-adapted rendering, with optional per-instrument SoundFonts.
• Specialized virtual keyboards that match each instrument (fretboard, drum pad, harp, accordion…).
• Lighting control synced to playback, from simple LED strips to professional DMX.
• Turn audio into MIDI — drop a recording in and get an editable MIDI file, entirely offline (optional; the engine is installed on demand).
• Built to run on its own: offline-first, one-click WiFi hotspot, one-button full system update, tablet-ready UI, 28 languages.

Connect any instrument

     

Whatever you built, there's a way in:

• USB MIDI — automatic detection and hot-plug.
• Bluetooth LE MIDI — scan and pair wireless instruments; inbound BLE notes are routed like any other input.
• Network MIDI (RTP-MIDI) — experimental. Connect over WiFi or Ethernet. The current RTP-MIDI session is a simplified, not-yet-conformant AppleMIDI implementation (no invitation handshake, clock synchronisation or journal/recovery) and is not guaranteed to interoperate with macOS Network MIDI or other AppleMIDI peers yet. Reported as degraded on the health endpoint.
• Physical MIDI IN/OUT via GPIO — wire real 5-pin MIDI to the Raspberry Pi at 31250 baud using a MIDI HAT or a simple DIY circuit. Multiple hardware UARTs are supported (up to 6 on a Pi 4), with Running Status and SysEx, and a bounded, back-pressured write queue on output. See docs/GPIO_MIDI_WIRING.md for HAT and DIY wiring.

Capability health. Optional transports load only when their native dependencies are present, so a running server may not expose every transport above. Query GET /api/capabilities (or the capabilities block in /api/health) for the live ready / degraded / failed / disabled status of each subsystem.

File support. Standard MIDI files in format 0 and 1 with PPQ timing are supported, including SysEx (GM/GS/XG resets, Master Volume). Format 2 and SMPTE (frame-based) timing are explicitly rejected rather than played with an incorrect chronology.

Each instrument gets its own settings — note range, polyphony, type, latency, tuning and more — defined once and persisted.

Drive a whole orchestra

Point the system at a standard MIDI file and it does the conducting for you:

• Automatic channel routing — each MIDI channel is analysed (melody, bass, harmony, drums) and assigned to the most compatible connected instrument, with a single channel split across several instruments when needed.
• Automatic file adaptation — notes outside an instrument's range are transposed or folded back in, polyphony is reduced to what the instrument can play, and General MIDI drums are remapped to the available pads.
• Up to 16 instruments simultaneously — the full 16 MIDI channels, played together.
• Per-device latency compensation — measure each instrument's real delay (including a microphone-based calibration) so everything lands on the beat.
• Optional MIDI clock — keep clock-driven instruments locked to the tempo.

Play, loop & arrange

• Play live from the virtual keyboard, also reachable from the Loop manager's Live tab.
• Build loops and arrangements in the Loop manager: a searchable Library, a trigger Pad, a Live performance view, and a multi-track Arranger timeline.
• Preview before you commit — listen to any loop or MIDI file and switch between the original (General MIDI) sound and the instrument-adapted rendering.
• Realistic previews — assign a custom SF2 SoundFont to an instrument so the preview sounds closer to the real thing.

Specialized virtual keyboards

The on-screen keyboard adapts to the selected instrument instead of always showing piano keys — so playing and editing matches how the real instrument works.

Layouts include standard piano, string fretboards, drum/percussion pads, harp, accordion, harmonica, mallets, kalimba, steel drum and more — chosen automatically from each instrument's capabilities.

Built-in MIDI editor

A multi-mode editor with four specialized views over a shared transport and per-channel routing:

• Piano Roll — add / move / resize notes, 16 coloured channels, snap grid.
• Tablature — string instruments with bidirectional MIDI ↔ tab conversion.
• Drums — grid-based GM drum pattern editor.
• Wind — articulation and breath dynamics for wind instruments.

A dedicated touch mode (separate Move / Add / Resize controls) makes it usable on tablets. See docs/MIDI_EDITOR.md.

Audio → MIDI

Have a recording but no score? Drop the audio in and get a MIDI file in the library, ready to edit, adapt and play on the orchestra like any other.

• Anything FFmpeg reads — .wav, .mp3, .flac, .ogg, .m4a, .aac, .aiff, and the audio track of a .mp4 / .mkv / .webm.
• Runs on the Pi, offline — the transcription engine is a local program, not a cloud service; nothing leaves the box.
• Optional and opt-in — the feature is off until you enable it, and no model is ever downloaded without showing you its licence first. GMB ships no AI model.
• Musical, not literal — pitch bend and breath dynamics are preserved, ghost notes and duplicates are cleaned up, and three presets (Raw / Balanced / Clean) decide how much tidying happens.
• Straight into the library — the result lands in the same place as an uploaded MIDI file, so the editor, the auto-assigner and playback all work on it unchanged.

Drop an audio file anywhere on the interface — or pick one from the file browser — and the conversion opens with that file ready to go. See docs/AUDIO_TRANSCRIPTION.md.

Lighting

Stage and ambient lighting synchronized with MIDI playback, driven straight from the Raspberry Pi:

• GPIO LED strips (WS2812/NeoPixel and on/off pins), plus ArtNet DMX, sACN/E1.31, OSC, HTTP/WLED and MQTT drivers.
• A rules engine with MIDI-learn: trigger colour and brightness from note ranges, velocity and CC values.

Built to run on its own

This is meant to live on a Pi backstage, not next to a developer's laptop:

• Offline-first — all sounds and assets are stored locally; no internet needed at runtime.
• One-click WiFi hotspot — turn the Pi into its own access point from the System settings modal (SSID, password, band), with a captive portal so a tablet connects straight to the interface.
• One-button full system update — update the whole system in a few minutes from the settings, with live progress and automatic restart.
• Touchscreen / tablet ready — responsive, multi-touch UI.
• 28 languages, including translated MIDI instrument names: English, French, Spanish, German, Italian, Portuguese, Dutch, Polish, Russian, Chinese, Japanese, Korean, Turkish, Hindi, Bengali, Thai, Vietnamese, Czech, Danish, Finnish, Greek, Hungarian, Indonesian, Norwegian, Swedish, Ukrainian, Esperanto, Tagalog.

Roadmap / in progress

The project already includes tooling for hand and finger management on string and keyboard instruments — hand-position editing, feasibility simulation and finger/fret visualization — used to keep adapted parts physically playable.

Planned evolutions:

• MIDI-message-driven lighting on instruments and peripherals — extend lighting control so the instrument's own lights respond to MIDI.
• Humanoid-hand control — drive robotic hands for string and keyboard instruments. See docs/HUMANOID_HAND_MANAGEMENT.md and docs/HAND_VISUALIZATION.md.

Development

Prerequisites: Node.js >= 20.0.0.

git clone https://github.com/glloq/General-Midi-Boop.git
cd General-Midi-Boop
npm install

Common commands:

• npm run dev — development server with hot reload
• npm start — production server
• npm test — backend tests (Jest)
• npm run test:frontend — frontend tests (Vitest)
• npm run lint — ESLint
• npm run format — Prettier
• npm run build — Vite production build

Deployment options: direct Node.js (npm start), PM2 for production with auto-restart, or Docker (docker-compose up -d). See docs/INSTALLATION.md.

Documentation

• Project Wiki — guided tour, usage, troubleshooting (sources tracked in wiki/)
• Installation Guide
• Architecture
• API Reference
• Auto-Assignment System
• GPIO MIDI Wiring
• MIDI Editor
• Audio → MIDI Transcription
• SysEx Identity Protocol
• Contributing
• Changelog

compatible instruments/code for ESP32

• Servo Flute GMB
• Drums Engine GMB
• Servo Plucked Strings GMB
• Stepper Plucked Strings GMB
• PlayMode-GMB

soon to come

• Accordion-servo-midi
• harmonica_Midi
• trumpet
• servo-Melodica-GMB
• slide_Whistle-GMB
• Servo-bowed-strings-GMB
• stepper-bowed-string-GMB

compatible instruments/code for Arduino (kind of deprecated/not really fully done)

• Ukuletron
• stepper-midi-4-cords-instrument
• 16-cords-lyre-midi
• servo-midi-music
• Orchestrion_Piano
• Orchestrion_FlutePan

License

The source code is released under the MIT License — see LICENSE.

Everything else that ships with a build has its own terms:

• npm dependencies (271 runtime packages, all permissive) — THIRD-PARTY-NOTICES.md, regenerated by node scripts/audit/licenses.mjs --emit.
• Icons, soundfont, vendored browser libraries — assets/ASSET-LICENSES.md.

Before you redistribute a build, read assets/ASSET-LICENSES.md. Two items are unresolved as of 2026-09-08: public/lib/WebAudioFontPlayer.js is fetched at install time from an upstream that is now GPL-3.0-or-later, and 57 of the shipped icons came through SVG Repo with no traceable licence. Neither is covered by the MIT licence above.