A next-generation Digital Audio Workstation combining:

• JUCE 8.x (C++) for rock-solid audio engine & plugin hosting
• egui 0.31 (Rust) for immediate-mode reactive UI
• Rust FFI Bridge for seamless realtime-safe interop
• Python scripting (PyO3) for automation & extensibility

Requirements:

• Rust 1.70+
• CMake 3.22+
• JUCE 8.0.4 (auto-downloaded via CMake FetchContent)
• libflac, libvorbis, ALSA (Linux)

Build:

# Build Rust FFI bridge (creates static lib)
cargo build --release -p rysyn_ffi_bridge
# Build JUCE audio core
cd apps/juce_core
mkdir build && cd build
cmake ..
cmake --build . -j$(nproc)
# Run egui UI
cd ../.. && cargo run --release --bin rysyn

Test audio core:

# Standalone JUCE app - initializes audio, scans plugins, tests transport
./apps/juce_core/build/rysyn_juce_core_artefacts/rysyn_juce_core

Golden Rule: UI never touches realtime threads

1. Per-Frame Snapshot (UI Read-Only)

   • Every frame, UI calls rysyn_get_state_json()

   • Receives JSON snapshot of entire DAW state:

     {
      "transport": {
      "is_playing": true,
      "playhead_beats": 24.5,
      "bpm": 120.0,
      "tempo": 120.0
      },
      "tracks": [
      {
      "id": 1,
      "name": "Kick",
      "volume": 1.0,
      "pan": 0.0,
      "is_muted": false,
      "is_selected": false,
      "plugins": ["AIDA-X", null, null, null, ...]
      }
      ],
      "meters": {
      "master_l": 0.45,
      "master_r": 0.42,
      "track_levels_l": [0.32, 0.18, 0.0, ...]
      },
      "available_plugins": [
      {"id": "Cardinal", "name": "Cardinal", "format": "VST3", ...},
      {"id": "SurgeXT", "name": "Surge XT", ...}
      ]
     }

   • UI renders based on this snapshot (no state mutations)

   • Metric updates (VU meters, playhead) appear smoothly

2. Command Queue (UI → Audio)

   • User clicks "Play" → UI sends JSON command:

     {"Play": null}

   • User changes BPM → UI sends:

     {"SetTempo": {"bpm": 140.0}}

   • Commands are serialized via serde, sent through rysyn_send_command_json()

   • Queued in crossbeam channel (lockfree MPMC)

3. JUCE Message Thread (Command Processing)

   • JUCE timer fires every ~16ms (on message thread, NOT audio thread)
   • Calls rysyn_recv_command_json() repeatedly
   • Parses each command JSON and dispatches:
     • Play → audioCore->play()
     • SetTempo → transport->setBpm()
     • LoadPlugin → track->loadPlugin(slotId, pluginId)
     • etc.
   • After processing, calls rysyn_update_state_json() with fresh state

4. Realtime Audio Thread (Read-Only)

   • Audio callback: AudioSource::getNextAudioBlock()
   • Reads ONLY: - Atomic<bool> playing - Atomic<double> bpm, playheadBeats - Mutable track mix controls (already atomic)
   • Produces audio + updates peak meters (atomics)
   • ZERO allocations, ZERO locks

✅ Completed

• Audio device I/O (ALSA on Linux, CoreAudio on Mac, WinMM on Windows via JUCE)
• VST3 plugin scanning & hosting (84 plugins found: Cardinal, Surge XT, Dexed, etc.)
• Transport (play/pause/stop, BPM, loop region, playhead seek)
• Track management (create/delete, volume/pan/mute/solo)
• egui UI layout (Transport, Timeline, TrackList, Mixer, Browser, Inspector panels)
• FFI bridge (C exports + Rust internals)
• JSON state serialization (serde_json)
• Command queue (crossbeam-channel)
• Python scripting skeleton (PyO3 bindings ready)

⏳ TODO (Post-MVP)

• Audio clip playback + MIDI sequencing
• Recording (mic input → clips)
• Offline rendering
• Project save/load (.rysyn format)
• MIDI I/O + controller mappings
• Audio editing (time-stretching, pitch, etc.)
• Undo/Redo system
• Preferences + audio device selection UI
• Keyboard shortcuts
• Plugin presets
• Track/clip coloring + naming
• Meter/analyzer tools
• Built-in effects (EQ, Compressor, Reverb)

Audio Core Standalone Test

./apps/juce_core/build/rysyn_juce_core_artefacts/rysyn_juce_core

Output:

Audio Core initialized successfully!
Sample Rate: 44100 Hz
Buffer Size: 512 samples
Added track with ID: 1
Scanning for VST3 plugins...
Found 84 plugins:
 - AIDA-X (AIDA DSP)
 - Cardinal (DISTRHO)
 - Dexed (Digital Suburban)
 - Surge XT (Surge Synth Team)
 ... and 80 more
Starting playback test (BPM: 120)...
Playback stopped.

UI Build

cargo build --release --bin rysyn
# Runs immediately with all UI panels visible
# Transport responsive: play/pause buttons work
# Track list: can see default track
# Mixer: volume/pan controls present
# Browser: plugin list loads from JUCE state

Python Scripting (Post-MVP)

import rysyn
# Transport
rysyn.play()
rysyn.set_bpm(140.0)
rysyn.set_loop_region(0.0, 8.0)
rysyn.stop()
# Tracks
rysyn.create_track("Bass", is_midi=True)
rysyn.set_track_volume(track_id=1, volume=0.8)
# Plugins
plugins = rysyn.get_plugins()
rysyn.load_plugin(track_id=1, plugin_id="Surge XT", slot=0)
# State inspection
state = rysyn.get_state()
print(state["transport"]["bpm"])

1. Why JUCE? - Battle-tested audio I/O across Windows/Mac/Linux - VST3 hosting built-in (same code works everywhere) - Lightweight compared to full framework overhead - Used by REAPER, Bitwig, Ableton internals
2. Why egui (Rust)? - Immediate-mode = easy to sync with async state - Blazing fast iteration (no borrow checker headaches on UI) - Integrates seamlessly with Rust ecosystem - Alternative: C++ UI in Qt, but then lose Rust benefits
3. Why JSON for state/commands? - Human-readable debugging - Extensible (add fields without breaking ABI) - Easy to script/log/replay - Same approach as REAPER's action system
4. Why FFI instead of embedding? - Clean boundary: audio core is C++, UI is Rust - Either can be replaced/upgraded independently - Plugin presets, configs can be pure JSON - Easier to test each layer separately
5. Why not lock-free everywhere? - Message thread already has 16ms latency budget (safe for commands) - Audio thread only reads atomics (zero overhead) - Simplifies implementation vs. wait-free queues

Phase 1 (MVP - Current)

• [done] Audio core + VST3 hosting
• [done] Basic UI framework
• [done] Command/state system
• [WIP] Audio playback (in progress)

Phase 2 (Beta)

• Recording
• MIDI sequencing
• Clip editing
• Project save/load

Phase 3 (v1.0)

• Complex time-stretching
• Built-in effects suite
• Advanced plugin routing
• Undo/Redo
• User presets

See CONTRIBUTING.md (coming soon)

MIT License - See LICENSE file

Inspired by REAPER's architecture and Bitwig's cross-platform approach.