ALM Busy Circuits MCO (mk II) (2024–)

A six-inch portal to the soul of 90s digital synths, reborn with a color screen and seven voices that still feel like cheating

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.

What makes the MCO (mk II) stand out isn’t just the sheer variety, but how each engine commits to its era. The BC8000 mode doesn’t just approximate supersaws—it nails the way those Roland waves wobble and breathe, complete with unison detune that spreads like warm butter across your stereo field. The Sylon vocoder doesn’t just gate noise—it lets you route external signals, modulate formants in real time, and build robotic choirs that feel ripped from a forgotten Autechre B-side. And the Oomph engine? That’s where you go when you need a kick that doesn’t just hit but collapses the room, 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 not building monophonic leads so much as sculpting harmonic events. It’s not a traditional VCO replacement; it’s a synth voice in a box, and it wants to be the centerpiece of your patch, not just another oscillator in the stack.

Despite the complexity, ALM didn’t drown the interface in jacks and buttons. There’s a single encoder, a bright color display, and three CV inputs that can be assigned across engines and parameters. The UI, while menu-dense, is logically laid out—more like a modern synth workstation than a patchable module trying to hide its digital guts. You can save presets, recall chords, and even upload custom wavetables via USB-C. It remembers your settings. It boots fast. It doesn’t crash. These might sound like low bars, but in the Eurorack world, where firmware bugs can turn a dream module into a paperweight, reliability is its own kind of magic. And yes, it’s firmware-upgradable—ALM has a track record of meaningful updates, not just bug fixes. This thing will likely get better with age, not worse.

Specifications

Key Features

A Display That Doesn’t Lie

The color screen on the MCO (mk II) is more than a convenience—it’s 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’re not guessing—you’re seeing. The UI follows a consistent hierarchy: engine select, parameter browse, value adjust. It’s not flashy, but it’s fast. And because it retains settings, you’re not relearning your patch every time you power up. This is a module that respects your time.

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 legacy of the original MCO, with user-loadable wavetables and smooth scanning. ToneSum is a deep additive synth with 12 operators, capable of bell-like tones or evolving pads that shimmer with inharmonic grit. BC8000 is pure 90s euphoria—supersaws, unison stacks, and that distinctive Roland digital sheen. Virtana delivers warm, slightly gritty virtual analog that avoids the sterility of early VA synths. Sylon turns the module into a vocoder, complete 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. And the SID GUTs engine? That’s pure nostalgia—authentic 6581/8580 chip tones, complete with filter nonlinearities and that unmistakable bite. Each engine has its own character, its own workflow, and its own sonic footprint.

Polyphony Without the Patch Cables

In a world where polyphony often means stacking oscillators or using external sequencers, the MCO (mk II) builds it 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. This isn’t just for chords—it’s for building harmonic movement within a single module. Want a supersaw arpeggio that shifts from major to diminished? Program it. Need a vocoder phrase that cycles through three inversions? Done. 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 simultaneously—but that’s a fair trade for the density. It’s not a full polyphonic synth, but it’s close enough to feel like one.

Historical Context

The MCO (mk II) exists at a crossroads. Eurorack, once dominated by analog oscillators and modular purism, has embraced digital complexity with open arms—but not always gracefully. Many digital modules feel like software ports, lacking the immediacy of hardware. 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 while doubling down on 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 stands apart by focusing not on generative textures, but on recognizable, era-specific sounds. Where Plaits explores abstract timbres, the MCO (mk II) wants you to hear the 90s. It’s a nostalgic module, yes, but not a retro one. It doesn’t emulate—it resurrects.

ALM, known for complex, no-compromise designs like the Befaco East Coast Mixing Company and the Zorlon Cannon, has always catered to the tinkerer. The MCO (mk II) feels like their most accessible offering to date—not because it’s simple, but because it’s complete. It doesn’t require external envelopes, LFOs, or sequencers to sound full. It’s a statement: digital synthesis in Eurorack doesn’t have to be cold, academic, or patch-heavy. It can be lush, immediate, and fun. Competitors like Intellijel’s Metasonix-derived modules or Erica’s DSP-based synths offer similar density, but few match the MCO (mk II)’s breadth of voice types. It’s less a competitor to any single module and more a challenge to the idea that a Eurorack voice needs to be built from multiple parts.

Collectibility & Value

As of 2024, the MCO (mk II) is too new to be “vintage,” but it’s already on the radar of collectors who track ALM’s limited runs and firmware-driven evolution. 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 buyers should 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 quality is solid, with a metal faceplate, sturdy jacks, and a well-anchored encoder. The real risk isn’t hardware—it’s usability. This module demands engagement. If you’re the type who wants to twist knobs and hear immediate results, the menu diving might frustrate. But if you’re willing to learn its language, it pays back in sonic variety.

What to check before buying: ensure 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. Because it supports Axon expanders, some users may sell it without the expander—but the full potential isn’t unlocked without one. Also, while the dual outputs are a plus, they’re not 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; don’t expect daily patches. This is a module that rewards patience, not impulse.

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