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0x808

Drum machine & synth workstation — C engine, multi-frontend GUI

0x808 demo

Watch full demo video

A standalone drum machine, step sequencer, and synthesizer — also available as a VST3/CLAP plugin and a GTK 4.0 native Linux frontend. 72 bundled drum samples, 50 synth presets, pattern-based arrangement, and offline WAV/MP3 export. All dependencies vendored, zero external runtime dependencies.

Downloads

Pre-built binaries are available on the Releases page:

Platform Files
Windows Installer (.exe) or portable zip (standalone + VST3 + CLAP)
Linux Tarball (ImGui + GTK + plugins) or AppImage
macOS DMG (standalone .app) or zip (standalone + VST3 + CLAP)

Screenshots

GTK 4.0 Frontend (Vaporwave Theme)

0x808 GTK Frontend

ImGui Frontend

7 built-in themes (Dark, Light, Hacker, Midnight, Amber, Vaporwave, Neon) + user-defined themes via JSON files in the themes/ folder.

Features

  • Drum grid — 16-track step sequencer with velocity, pitch per step, mute/solo
  • Piano roll — melodic note editing with variable-length notes
  • 3 synthesis modes — subtractive, FM (4-op), and wavetable with 50 presets
  • SoundFont support — load .sf2 files via TinySoundFont
  • Sample browser — load WAV/MP3/FLAC samples, 72 bundled CC0 drum samples
  • Song arrangement — pattern chaining with song/perform modes
  • Effects — per-track and master bus filter, delay, reverb, overdrive, fuzz, chorus
  • Export — offline render to WAV (16/24/32-bit) and MP3 (128-320k)
  • Project save/load — JSON-based .sqproj format
  • Undo/redo — Ctrl+Z / Ctrl+Shift+Z with 32 levels
  • Swing/shuffle — per-transport swing control (0-100%)
  • Velocity humanization — per-track random velocity variation
  • Pattern presets — 12 drum patterns + 10 bass lines (House, Trap, DnB, Lo-fi, etc.)
  • Multiple frontends — ImGui (standalone + plugin) and GTK 4.0 (Linux native)

Frontends

Frontend Binary Platform Notes
ImGui Standalone 0x808 / 0x808.exe Linux, macOS, Windows SDL2 + OpenGL + Dear ImGui
GTK 4.0 0x808_gtk Linux Native GTK widgets + Cairo rendering
VST3 Plugin 0x808.vst3 Linux, macOS, Windows Embeds in DAW host window
CLAP Plugin 0x808.clap Linux, macOS, Windows Embeds in DAW host window
CLI 0x808_cli Linux, macOS, Windows Terminal-only audio engine

All GUI frontends share the sq_app controller library (C99) for keyboard shortcuts, panel state, playhead, and undo coordination. See docs/FRONTEND_FEATURES.md for the full feature parity specification.

Plugin Install Locations

Copy the built plugin files to the appropriate directory for your DAW to find them:

Format Linux macOS Windows
VST3 ~/.vst3/ ~/Library/Audio/Plug-Ins/VST3/ C:\Program Files\Common Files\VST3\
CLAP ~/.clap/ ~/Library/Audio/Plug-Ins/CLAP/ C:\Program Files\Common Files\CLAP\

The VST3 must keep its bundle structure: copy the entire 0x808.vst3/ directory, not just the inner file.

The Windows installer handles this automatically.

MIDI Input

USB MIDI controllers are supported on all platforms (ALSA on Linux, WinMM on Windows, CoreMIDI on macOS). Controllers are auto-detected on plug-in and auto-reconnected if unplugged and replugged.

Bluetooth MIDI limitation: Bluetooth MIDI is not directly supported. On Windows, the WinMM backend only sees USB/virtual MIDI ports. As a workaround, use loopMIDI to create a virtual port and MIDIberry (free, Microsoft Store) to bridge your Bluetooth MIDI device to the virtual port.

Default CC mappings (work out of the box with most controllers):

CC Parameter Controllers
1 Filter Cutoff (mod wheel) Universal
7 Master Volume Universal
70-77 Cutoff, Reso, Attack, Decay, Sustain, Release, Reverb, Delay Akai MPK Mini
21-28 Same as above Novation Launchkey
74 Filter Cutoff GM2 standard
71 Filter Resonance GM2 standard
91 Reverb Send GM2 standard

Custom mappings can be created via MIDI Learn: right-click any synth knob, then twist the controller knob to bind it.

Keyboard Shortcuts

Key Action
Space Play / Stop
1-9 Select pattern
+ New pattern
Ctrl+S Save project
Ctrl+O Load project
Ctrl+C Copy pattern
Ctrl+V Paste pattern
Ctrl+Z Undo
Ctrl+Shift+Z Redo
Ctrl+T Tap tempo
Ctrl+G Cycle theme
Escape Quit

Mouse Controls

Drum Grid (Step Sequencer)

Action Behavior
Left-click Toggle pad on/off (velocity 100)
Left-click + drag Paint pads on or off across the grid
Right-click (tap) Open velocity/pitch popup editor
Right-click + hold + drag left/right Adjust velocity in real-time
Right-click + hold + drag up/down Adjust pitch offset in real-time

Piano Roll

Action Behavior
Left-click Place or remove a note
Scroll wheel Scroll the view vertically

Virtual Keyboard

Action Behavior
Click keys Trigger synth notes
Click + drag Glissando across keys
QWERTY keys (when Piano panel is open) Play notes — Z-M = lower octave, Q-P = upper octave
<< / >> Shift keyboard octave range

Knobs

Action Behavior
Drag up/down Adjust value (full range ≈ 200 pixels)
Shift + drag Fine adjustment (10x precision)
Double-click Reset to default value

Toolbar Buttons

Action Behavior
Click PRESETS Toggle pattern presets dialog open/closed
Click EXPORT Toggle export dialog open/closed
Click THEME Open theme selector popup
Click panel buttons Toggle panel visibility (BROWSE, MIXER, PIANO, KEYS)

Building

Requirements

  • C11 compiler (GCC, Clang, or MSVC) — engine, app controller, and tests
  • C++17 compiler — ImGui GUI layer
  • CMake 3.16+
  • SDL2 (for GUI and audio)
  • OpenGL 3.3 (for ImGui targets)
  • GTK 4.0 (optional, for GTK frontend)

All other dependencies are vendored in deps/.

Linux

sudo apt install libsdl2-dev libgl-dev g++   # Debian/Ubuntu
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j$(nproc)

Linux with GTK Frontend

sudo apt install libsdl2-dev libgl-dev libgtk-4-dev g++
cmake -B build -DCMAKE_BUILD_TYPE=Release -DBUILD_GTK=ON
cmake --build build -j$(nproc)

macOS

brew install sdl2
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j$(sysctl -n hw.ncpu)

Windows (MSVC + vcpkg)

vcpkg install sdl2:x64-windows
cmake -B build -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=$env:VCPKG_INSTALLATION_ROOT/scripts/buildsystems/vcpkg.cmake
cmake --build build --config Release

Windows (MinGW cross-compile from Linux)

sudo apt install gcc-mingw-w64-x86-64 g++-mingw-w64-x86-64
cmake -B build_win -DCMAKE_TOOLCHAIN_FILE=cmake/mingw-w64.cmake
cmake --build build_win -j$(nproc)

Build Targets

Target Output Description
sequencer_gui 0x808 / 0x808.exe ImGui GUI (SDL2 + OpenGL + Dear ImGui)
sequencer_gtk 0x808_gtk GTK 4.0 GUI (optional, -DBUILD_GTK=ON)
sequencer_standalone 0x808_cli Terminal-only audio engine
sequencer_vst3 0x808.vst3 VST3 plugin
sequencer_clap 0x808.clap CLAP plugin

Running

# ImGui GUI
./build/0x808

# GTK GUI (if built with -DBUILD_GTK=ON)
./build/0x808_gtk

# Terminal mode
./build/0x808_cli

Testing

16 test targets covering DSP, synthesis, effects, project I/O, undo, edge cases, fuzzing, plugin loading, and snapshot regression.

# Run the full test suite
./scripts/test_all.sh

# Full mode includes AddressSanitizer + UBSan
./scripts/test_all.sh full

Architecture

+---------------------------------------------+
|  Layer 4: Host Wrappers                     |
|  Standalone | Plugin (VST3/CLAP) | GTK      |
+---------------------------------------------+
|  Layer 3: GUI Components                    |
|  ImGui (C++): grid, piano, knobs, etc.     |
|  GTK (C): Cairo drawing, native widgets     |
+---------------------------------------------+
|  Layer 2: App Controller (sq_app, C99)      |
|  Shortcuts, panel state, playhead, undo     |
+---------------------------------------------+
|  Layer 1: DSP Engine (pure C99, zero deps)  |
|  Sequencer, sampler, synth, mixer, effects  |
|  Input: transport state -> Output: float buf|
+---------------------------------------------+

The engine (Layer 1) has zero knowledge of GUI or audio drivers. The app controller (Layer 2) provides shared non-rendering logic used by all frontends. Audio runs on a separate thread from the GUI.

Bundled Samples

72 CC0 drum samples from classic machines:

  • TR-808 — bass drum, snare, clap, hi-hat, cowbell, cymbal, toms
  • TR-909 — bass drum, snare, clap, hi-hat, ride, crash, toms
  • TR-505 — bass drum, snare, hi-hat, toms, clap, rimshot
  • MRK-2 — kicks, snares, hi-hats, claps, toms
  • CR-78 / LM-2 — additional percussion

Synth Presets

50 built-in presets across 3 synthesis modes:

Subtractive: Bass, Pad, Lead, Pluck, Stab, plus classic-inspired presets (Moog, 303 Acid, Juno Pad, OBX Brass, Prophet Strings, ARP Lead, SH Rez, and more)

FM: Bell, E.Piano, Metal, Bass, Pad, DX Piano, DX Vibes, FM Organ, FM Marimba, FM Clav, FM Strings, FM Koto, FM Flute, FM Harmonics, DX Sitar

Wavetable: Sweep, Harmonic, PWM, Vocal, WT Glass, WT Wobble, WT Choir

Dependencies (vendored)

Library License Purpose
miniaudio Public Domain Cross-platform audio I/O
Dear ImGui MIT Immediate-mode GUI (C++)
dr_wav/dr_mp3/dr_flac Public Domain Audio file decoding
TinySoundFont MIT SoundFont2 synthesis
cJSON MIT JSON parsing for project files
RtMidi MIT Cross-platform MIDI I/O
Shine LGPL-2 Fixed-point MP3 encoder (opt-in)

MP3 Export (Optional)

MP3 export uses Shine which is LGPL-2. It is disabled by default to keep the core project MIT-clean. To enable:

cmake -B build -DENABLE_MP3=ON

Without -DENABLE_MP3=ON, WAV export works normally and MP3 export returns a friendly error message.

License

MIT — see LICENSE

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Drum machine & synth workstation — C11 audio engine, step sequencer, FM/subtractive/wavetable synthesis. Standalone (SDL2), VST3, CLAP plugin.

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Releases 6

v1.3.0 — Sequencer features, MIDI support, session auto-save Latest
Mar 18, 2026
+ 5 releases

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