ALM Busy Circuits MCO (mk II) (2024–)

A six-inch module with a color screen and seven voices, built on the sound of 90s digital synths

Overview

Fire up the MCO (mk II), and you’ll swear you’ve cracked open a time capsule sealed in 1997—only it’s been upgraded with a modern brain and a conscience. This isn’t just a wavetable oscillator with extra features bolted on; it’s a full digital voice module wearing the disguise of a 6HP Eurorack brick, and it plays dirty by packing seven distinct synthesis engines into one impossibly dense package. You get the original MCO’s DigiWave engine, yes, but now it’s flanked by a 12-operator additive monster, a JP-8000-style supersaw machine, a full vocoder, a SID chip emulator, a virtual analog engine with 90s FM radio warmth, and a dedicated bass synth that can shake mortar from brick. All of it lives behind a crisp, responsive color display and a single encoder that somehow doesn’t drive you insane. It’s the rare module that feels like it should be twice the size, yet somehow doesn’t just fit—it thrives.

Each engine commits to its era. The BC8000 mode does the supersaw wobble of those Roland waves, with unison detune that spreads across the stereo field. The Sylon vocoder takes external signals, modulates formants in real time, and builds robotic choirs that sound like a forgotten Autechre B-side. The Oomph engine is the kick and sub-bass voice, with sub-bass so deep it bypasses your ears and vibrates your spine. Polyphony is handled in chords - four-note per engine, with inversions and user-defined shapes - so you're sculpting harmonic events more than building monophonic leads. It's not a traditional VCO replacement. It's a synth voice in a box, and it wants to be the centerpiece of the patch.

ALM kept the panel simple. There's a single encoder, a bright color display, and three CV inputs that can be assigned across engines and parameters. The UI is menu-dense but logically laid out, more like a modern synth workstation than a patchable module. You can save presets, recall chords, and upload custom wavetables via USB-C. It remembers your settings. It boots fast. It doesn't crash. Those sound like low bars, but in the Eurorack world firmware bugs can turn a good module into a paperweight. It's firmware-upgradable, and ALM has a track record of meaningful updates, not just bug fixes.

Specifications

Key Features

A Display That Doesn’t Lie

The color screen is the reason this module doesn't feel like a labyrinth. Early digital modules often sacrificed usability for density, forcing users to memorize menu trees or rely on external software. Here, the display renders waveforms, parameter values, and engine status in crisp, readable detail. When you're tweaking formants in Sylon or drawing harmonic spectra in ToneSum, you can see what you're doing. The UI follows a consistent hierarchy: engine select, parameter browse, value adjust. It's not flashy, but it's fast. Because it retains settings, you don't have to rebuild your patch every time you power up.

Seven Engines, Seven Personalities

Most multi-engine modules offer variations on a theme - different filters, slight waveform tweaks. The MCO (mk II) gives you seven distinct instruments. The DigiWave engine carries forward the original MCO, with user-loadable wavetables and smooth scanning. ToneSum is an additive synth with 12 operators, capable of bell-like tones or evolving pads with inharmonic grit. BC8000 is the 90s supersaw engine, with unison stacks and that distinctive Roland digital sheen. Virtana is a warm, slightly gritty virtual analog that avoids the sterility of early VA synths. Sylon turns the module into a vocoder, with carrier and modulator routing, formant shifting, and noise injection. Oomph is a kick and sub-bass specialist, with pitch envelopes and body controls that make it punchier than most dedicated drum modules. The SID GUTs engine does 6581/8580 chip tones, with filter nonlinearities and that unmistakable bite. Each engine has its own workflow and its own sound.

Polyphony Without the Patch Cables

Polyphony is built in. Each engine supports four-note chords, with predefined shapes (major, minor, etc.) and four user-programmable chords. You can invert them, transpose them, or modulate them via CV. That makes harmonic movement possible inside a single module. A supersaw arpeggio that shifts from major to diminished is a matter of programming it. So is a vocoder phrase that cycles through three inversions. The polyphony is fixed per engine, not freely assignable across voices, so you can't mix a 3-note chord in BC8000 with a 1-note bass in Oomph at the same time. It's not a full polyphonic synth.

Historical Context

The original MCO, released years earlier, was a cult favorite for its raw wavetable power, but it demanded deep patching and had no display. The mk II answers those limitations and keeps what made the first version special: density, character, and a refusal to pick a single synthesis method. It arrives alongside a wave of "Swiss Army knife" modules, from Mutable Instruments' Plaits to Noise Engineering's Loquelic Iteritas, but it focuses on recognizable, era-specific sounds instead of generative textures. Where Plaits explores abstract timbres, the MCO (mk II) goes for the 90s. It's a nostalgic module, but not a retro one.

ALM is known for complex, no-compromise designs like the Befaco East Coast Mixing Company and the Zorlon Cannon, and has always catered to the tinkerer. The MCO (mk II) is their most accessible offering to date, not because it's simple, but because it's complete. It doesn't need external envelopes, LFOs, or sequencers to sound full. Competitors like Intellijel's Metasonix-derived modules or Erica's DSP-based synths offer similar density, but few match its breadth of voice types.

Collectibility & Value

As of 2024, the MCO (mk II) is too new to be "vintage," but collectors who track ALM's limited runs and firmware-driven evolution already have it on the radar. Priced at €299, it sits in the upper mid-tier for digital modules - more than a Plaits, less than a full standalone synth. Condition matters less than firmware version. Early units may lack features that arrive in updates, so verify firmware before purchasing. Used units appear on Reverb and forums at 10-20% below retail, but stock moves quickly. There are no known hardware failures at this stage - no capacitor issues, no display defects, no power regulation problems. The build is solid, with a metal faceplate, sturdy jacks, and a well-anchored encoder. The real risk is usability. If you want to twist knobs and hear immediate results, the menu diving might frustrate.

What to check before buying: make sure the display is fully responsive, test all engine types for audio glitches, verify USB-C connectivity for updates, and confirm that CV modulation works across assigned parameters. It supports Axon expanders, so some users may sell it without the expander, and the full potential isn't unlocked without one. The dual outputs aren't always independently useful. In most engines they offer the same signal (sometimes with slight processing differences), so don't expect true stereo separation out of the box. Maintenance is minimal - no moving parts, no analog calibration - but firmware updates are essential. ALM's support is active, but not instant.

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