InterzoneXXL v0.1.1

Valley Audio's Interzone synth voice, played from MIDI in mono or poly and patched with its own LFOs, random sources and sequencers, running natively inside MPC OS on the Akai Force.

InterzoneXXL is a VST2 instrument for MPC OS's built-in plugin host, made by L'Cronx (shown on the device as InterzoneXXL by L'Cronx). It is a port of Interzone, Dale Johnson's classic monosynth voice for VCV Rack: a VCO with glide, pitch modulation, pulse-width modulation and a sub wave, a mixer with noise, a resonant 2/4-pole OTA filter with a high-pass, an LFO with seven waves, a looping envelope and a VCA. The pages are the module's panel, drawn from Valley's own artwork, sliders where the module has sliders, knobs where it has knobs, switches where it has switches. On VCV Rack, Interzone comes alive through what is patched into its jacks; a Force has no cables, so, as in PlateauXXL, every input jack picks a source running inside the plugin.

Note

Status: 0.1.1, tested on an Akai Force (MPC OS 3.9.1 with MockbaMod). Offline, the plugin's output is also compared, sample for sample, with Valley's own Interzone module code fed the same notes and the same patch cables (x86, ASan + UBSan). Report anything odd under Issues.

The pages, rendered offline from the skin (on the device MPC fills in the values).

Highlights

• Interzone, the voice: Valley's own DSP (VecDirectOsc, VecOTAFilter, VecLoopingADSR, DLFO), and the module's process() re-written for MPC OS line by line. The tests check the result against the module itself.
• Mono or Poly: Mono is one voice, last-note priority, Legato (glide between held notes, no retrigger) or Retrigger. Poly is Interzone's own polyphony (its DSP runs four voices per SIMD group) with 1 to 16 voices, the oldest note stolen when they are all busy. Pitch bend (0-24 semitones) and the sustain pedal work in both.
• The module's panel: VCO, FILTER / LFO and MIXER / ENV pages, each a piece of Interzone's dark panel with Valley's sliders, Rogan knobs and VCV's switches at the module's own positions; values above the sliders.
• Every input jack patched: VOct 2, PWM, Mixer Ext, Filter Freq 1 and 2 (with the module's blue attenuverters), Res, VCA Level (with its attenuverter), LFO Rate, Trig and Reset, Env Gate and Trig each pick a source and have an amount, on the CV IN page, as if a cable were plugged in.
• The sources (PlateauXXL's): four Bogaudio LFOs, Tidal Modulator 2 (Mutable Tides 2), Random Sampler (Mutable Marbles), two 16-step CV sequencers and two 16-step gate sequencers, locked to the MPC tempo if you like; plus Interzone's own output jacks (its LFO's seven waves, the envelope + and -, the VCO's saw, pulse and sub, per voice in Poly), MIDI velocity, mod wheel and pressure.
• Ext Osc: a simple oscillator per voice that follows the played note (saw, square, triangle, sine or noise, -3 to +2 octaves, tune, width); it feeds Mixer Ext by default, so the Ext slider is a second oscillator or a sub. Patch it anywhere else too.
• A gate sequencer plays the voice: Env Gate's source gates the envelope even with no key down, Env Trig's retriggers held notes, Seq 1 / 2 into VOct 2 transposes: an internal sequenced synth.
• VOICE page: voice mode, poly voices, mono retrigger, bend range, output level, RMXXXL's brickwall limiter (Drive, Ceiling, Release) and Panic (one tap back to the defaults, every note off). EXT OSC and PRESETS (16 slots of your own) on the same tab.
• Q-Links: every control on a Q-Link (the Interzone pages read left to right, bank 1 = Q-Links 1-8, bank 2 = 9-16).
• Sample-accurate notes: sequenced notes start at their exact position in the audio block.

Requirements

• An Akai Force (first generation). Other first-generation MPC OS units (MPC Live / Live II, One, X, Key 61) should work but are untested.
• Root SSH access to the device, for example through MockbaMod. Stock MPC OS can't install third-party plugins.
• MPC OS 3.x. The skin uses the 3.x format.

Installation

Download InterzoneXXL-<version>-mpc-armv7.zip from Releases, or build it (below). Unzip it and follow the INSTALL.md inside. In short:

scp -r InterzoneXXL-<version> root@<device-ip>:/tmp/
ssh -t root@<device-ip> sh /tmp/InterzoneXXL-<version>/install.sh

The installer asks for confirmation (-y skips it), stops MPC (save your project first), copies the plugin to /sdcard/Synths/L'Cronx - VST - InterzoneXXL/, backs up and edits MPC.settings, and starts MPC again. Then load InterzoneXXL (manufacturer L'Cronx) as a plugin instrument on a track. uninstall.sh removes it. Presets go in /sdcard/InterzoneXXL Presets (created on the first save), outside the plugin folder, so they survive updates.

Building

Linux or WSL with Python 3 (+ Pillow, cairosvg), gcc and Zig (pip install ziglang pillow cairosvg). No Docker.

git clone --recursive https://github.com/sunskiefer/InterzoneXXL
cd InterzoneXXL
./build.sh                # build/arm/interzonexxl.so + the skin -> build/package/
test/run_tests.sh         # the framework's host test + the engine against Valley's module, under ASan/UBSan
tools/device_bench.sh <device-ip>   # CPU on the device, Mono and Poly 16 (nothing is installed)

• tools/gen_params.py is the single source of the parameter list (params.json, src/param_ids.h). MPC stores automation by parameter index, so parameters are appended only.
• tools/panel.py places every control where the module has it; tools/layout.py writes layout.conf from it, and tools/panel_art.py draws the Interzone pages from Valley's and VCV's artwork (art/). The source pages come from PlateauXXL (tools/source_pages.py, tools/knob_art.py, tools/post_skin.py).

Related projects

• mpc-vst-plugins by sd88me: the framework InterzoneXXL is built on, and the plugin catalog.
• PlateauXXL and RMXXXL by the same author: the patching, the sources and sequencers, the presets, the limiter, Panic and the Q-Link handling come from them.
• ValleyRackFree, BogaudioModules and Audible Instruments: the VCV Rack modules InterzoneXXL ports.

License

InterzoneXXL is released under the GNU GPL v3.0 or later (LICENSE), as the Valley and VCV Rack code it includes. Third-party components keep their own licenses (below). The artwork includes VCV Component Library graphics (CC BY-NC 4.0), so InterzoneXXL is free and must not be sold.

Credits

• Interzone: Dale Johnson, Valley Audio (GPL-3.0-or-later). The DSP is vendored in third_party/valley with one local change, shared filter tables (VENDORED.md); the module's control layer is re-written for MPC OS in src/engine.cc.
• VCV Rack's SIMD and DSP headers: VCV (GPL-3.0-or-later), unchanged in third_party/rack (VENDORED.md).
• SIMDe: Evan Nemerson and contributors (MIT), the SSE-on-NEON layer Rack uses on ARM, in third_party/simde.
• LFO: Matt Demanett, Bogaudio (GPL-3.0-or-later), vendored unchanged in third_party/bogaudio.
• Tidal Modulator 2 and Random Sampler: Emilie Gillet, Mutable Instruments Tides 2 and Marbles (MIT), from VCV's fork of the eurorack code, in third_party/mutable; the module glue follows VCV Audible Instruments (GPL-3.0-or-later).
• Patching, sources, sequencers, presets, brickwall limiter, Panic, Q-Link handling: from PlateauXXL and RMXXXL by L'Cronx (GPL-3.0-or-later).
• VST2 wrapper, skin generator, installer: sd88me (mpc-vst-plugins) (MIT), as a submodule in third_party/mpc-vst-plugins.
• Artwork (art/): Interzone's panel, Valley's sliders and Rogan knobs (ValleyRackFree), VCV's switches and Rogan knobs (VCV Component Library, CC BY-NC 4.0), Bogaudio's knobs (CC BY-SA 4.0); see art/README.md.
• Interface font: Titillium Web, SIL Open Font License 1.1.

InterzoneXXL is not affiliated with or endorsed by Valley Audio, Bogaudio, Mutable Instruments, VCV or Akai Professional.