Guitar RackCraft

A real-time guitar effects processor for Android. Hosts 120+ LV2 audio plugins in a chainable rack interface with low-latency audio via Oboe and native plugin UIs rendered through a custom X11/EGL emulation layer.

It also includes experimental support for hosting Windows VST2/VST3 plugins (x86/x64) directly on-device via Wine + FEX emulation (see Windows VST plugins).

Features

• Chain multiple LV2 plugins with drag-and-drop reordering
• Real-time audio processing with low-latency Oboe I/O
• Native X11 plugin UIs rendered on Android via custom X11 server + EGL
• Host Windows VST2/VST3 plugins (x86/x64) via Wine + FEX emulation - see Windows VST plugins
• Neural amp modeling (NAM, AIDA-X)
• WAV file playback through the effects chain
• Audio recording (raw input + processed output)
• Preset save/restore

Requirements

• Android 8.0+ (API 26), arm64-v8a
• JDK 17
• Android SDK (API 35, NDK 27.2.12479018, CMake 3.22.1)
• System packages: ninja-build meson python3 python3-mako pkg-config autoconf automake libtool gettext patch cmake flex bison ocaml ocamlbuild ocaml-findlib libnum-ocaml-dev

./build.sh check verifies the host tools and the pinned NDK.

Build

# Initialize submodules
git submodule update --init --recursive

# Build native libraries (./build.sh help lists the steps, e.g.
# ./build.sh native neuralrack_done to rebuild and restage one plugin)
./build.sh

# Build and install debug APK
./run.sh debug

# Build release APK + AAB
./run.sh release

# Build Play Store AAB with asset packs
./run.sh playstore

Build flavors

Flavor	Description
full	All plugins bundled in a single APK
playstore	Plugins split into asset packs (gxplugins, neural, brummer) for Play Store delivery

Adding a plugin

See docs/adding-a-plugin.md.

Architecture

• Kotlin/Compose - Android UI layer
• C++17 - Audio engine, LV2 host, X11 server
• Oboe - Low-latency audio I/O
• lilv - LV2 plugin loading and management
• Cairo, EGL/GLES2 - rendering for plugin UIs
• X11 emulation - Custom minimal X11 server bridging native plugin UIs to Android surfaces

See 3rd_party/README.md for the full list of dependencies.

Windows VST plugins

In addition to the bundled LV2 plugins, the full flavor can host Windows VST2/VST3 plugins (32-bit x86 and 64-bit x64) directly on Android - no PC required. Each plugin runs inside a bundled Windows compatibility layer:

• Wine provides the Win32 API and PE loader, so the plugin's .dll / .vst3 loads unmodified.
• FEX-Emu JIT-translates the plugin's x86/x64 machine code to ARM64.
• The plugin editor is bridged through the same custom X11 server onto an Android surface; DXVK → Turnip (Mesa Vulkan on Adreno) translates Direct3D 11 plugin GUIs.

Import a plugin with the in-app VST manager (point it at a .dll or .vst3). Imported plugins appear under the Windows VST group in the plugin browser - tagged with format (VST2/VST3) and architecture (x86/x64) badges - and chain alongside LV2 plugins like any other effect.

Windows VSTs run under emulation, so they use more CPU than native LV2 plugins, and plugins that require online or hardware DRM activation may not work. The Windows VST host is built only in the full flavor (HAS_VST_HOST=true); the playstore flavor omits it.

License

GPLv3 - see LICENSE.