ALM Akemie's Castle (2015–)

An FM synth with knobs. It sounds like your Sega Mega Drive got patched into a modular rig.

Overview

Turn on a patch, twist a single knob, and the whole thing lurches into a metallic scream. This is not polite retro FM. It is FM wired straight into a Eurorack system, snarling and unpredictable. The ALM Akemie's Castle doesn't simulate vintage FM. It uses actual new-old-stock Yamaha FM chips, the same kind that powered SoundBlaster cards and the DX21, to make its sound. It's a dual-oscillator module, and each oscillator is a full four-operator FM voice, with six algorithms, eight waveforms per operator, feedback routing, and full CV control over nearly every parameter. You can dial in glassy pads with digital grit, or crank it into rhythmic noise storms that sound like a Game Genie glitching out on a forgotten ROM. And you can see what you're doing - no membrane buttons, no hidden menus, just 13 real knobs, a blue algorithm button, and attenuverters everywhere you need them.

Before this, FM in modular meant either clunky digital emulations or DIY FPGA projects that required firmware tweaks just to make a sine wave. ALM took the raw output of the Yamaha YM262 - a chip never meant for modular use - and built a tactile interface around it. The chip dates back to the late '80s, but it responds to CV and real-time modulation as if it had been waiting for modular all along. It's a full FM voice generator, split across two independent outputs, each able to run different algorithms, tunings and modulations. You can run both sides as self-contained two-operator FM synths, or chain them into four-operator voices. Oscillator A adds a chord mode that lets you dial through 16 preset voicings, from triads to dense clusters, with voltage-controllable inversion. Patch in a sequencer, modulate the chord input with a slow LFO, and your bassline starts shifting harmonies on its own.

This is not a polished, pristine FM experience. It's raw. There's aliasing, especially in the high end, a sizzly digital "fur" that clings to the waveform like static. The chip doesn't update levels smoothly. Sweep the operator level with a knob or CV and you hear stair-stepped zipper noise, a series of tiny clicks that can be distracting on pads or slow attacks. That's a hardware limitation of the YM262, and you either work around it or live with it. Many users route the output through an external VCA for smoother amplitude control, or low-pass filter the signal to tame the edge. There are also no envelope generators onboard, so the module expects you to have a system ready to drive it. No EGs, no LFOs, no memory. What you patch is what you get, and if you power down, you start fresh.

Specifications

Manufacturer	ALM Busy Circuits
Production Years	2015–
Original Price	£510 GBP
Format	Eurorack
HP	38
Depth	32mm
Power	+12V @ 120mA, -12V @ 60mA
Oscillators	Dual 4-operator FM
Operators per Oscillator	4
Algorithms	6
Waveforms per Operator	8 (including sine, square, saw)
Feedback	Independent per oscillator
Chord Mode	Oscillator A only, 16 presets, up to 5 voices
CV Inputs	Multiple per operator (frequency, level, algorithm, feedback, chord inversion)
Attenuverters	On most CV inputs
Outputs	Dual independent audio outputs (A and B)
FM Core Chip	Yamaha YM262 (new-old-stock)
Reverse Polarity Protection	Yes
Weight	Approx. 500g
Manual	Available via ALM website

Key Features

The Yamaha YM262: Ghost in the Machine

At the heart of Akemie's Castle is the Yamaha YM262, a chip originally designed for computer sound cards in the late 1980s. It's not a modern FPGA or a soft-synth core. It's the real thing, pulled from old stock. The chip was used in AdLib and SoundBlaster cards, and later found its way into budget Yamaha synths like the DX21 and DX100. Its sound is not as polished as the DX7. It's grittier and more aggressive, and it leans into the digital artifacts rather than hiding them. The Castle runs the chip in a way that bypasses its original MIDI limitations, putting every parameter under 1V/Oct and CV control. That means you can modulate operator levels, feedback amounts, and even algorithm selection in real time, which no vintage Yamaha could do without major hardware mods. The chip's polyphony is repurposed too. It was designed for multiple voices, and ALM uses it to run two independent FM oscillators, each with full four-operator architecture.

Knobs, Not Menus

FM synthesis has long meant opaque menus and tiny LCDs. On Akemie's Castle, every major parameter has a dedicated knob. Want to change an operator's waveform? Turn a knob. Adjust its level? Another knob. Modulate that level with an LFO? Patch it in and tweak the attenuverter right next to the input. The front panel is dense but logical, with each operator's controls grouped vertically so you can trace signal flow by eye. The algorithm is selected with a clicky blue push-button that cycles through the six options, with a small LED showing position. No touchscreen, no shift functions, just direct access. You can tweak a sound in real time, hear the changes instantly, and build patches by intuition rather than memorization.

Chord Mode: Harmony in a Knob

Oscillator A's chord mode is one of the module's sleeper features. Instead of generating single notes, it can play up to five-voice chords, selected with a rotary knob holding 16 presets. These range from standard triads to more exotic voicings, and each can be inverted using a CV input with attenuverter. Patch in a sequencer or random voltage, and the harmony shifts under the melody. It's not a full chord memory system. Combined with the FM engine's metallic, bell-like tones, it gives cinematic textures. The chord function is only on Output A, so Output B is free for a completely different FM voice, say a bass or a percussive hit. That makes the module effectively two synths in one.

Historical Context

Akemie's Castle launched in 2015, when FM synthesis was still largely a closed book in the modular world. The DX7 had become a vintage icon, but its menu-driven architecture didn't translate well to the hands-on approach of Eurorack. Most FM modules at the time were either simple two-operator designs or software-based emulations that lacked the bite of the original chips. ALM went straight to the source and used the actual silicon that defined a generation of video game and rave music. The modular boom was in full swing, and users wanted deep, complex sound sources. The Castle arrived alongside other digital modules like Mutable Instruments' Clouds and Make Noise's Mimeophon, but it offered full melodic and harmonic synthesis, not only texture. It also fit a broader Eurorack trend of reclaiming obsolete tech. New-old-stock chips, vintage DACs, and repurposed arcade hardware were becoming prized components. The YM262 wasn't just a cost-saving measure. It was a sonic choice that gave the Castle a character impossible to replicate with modern parts.

Collectibility & Value

New units still sell for around £510 GBP directly from ALM, and used prices hover between £400 - £480 depending on condition and market demand. It's not unobtainable, but it's consistently in demand, and stock tends to sell out quickly when restocked. Condition is generally straightforward, since there are no fragile membranes or delicate screens to fail. The main concern is the ribbon cable, which connects the front panel to the main board. Some early units had intermittent connections, though ALM has since improved the design. The module is reverse polarity protected, so accidental power mistakes won't kill it. The build is solid, with a black anodized aluminum panel and sturdy knobs. Because it uses a vintage chip, there are long-term questions about supply, but ALM has stated they have enough NOS stock to continue production for the foreseeable future. When those chips run out, the module will likely become a sought-after classic. The real cost is the system needed to drive it. Without at least a dual envelope generator and a few LFOs, the Castle will sit there making static tones. Many users pair it with ALM's own Pip Slope or O/A/x2, or third-party modules like the Intellijel Dual ADSR or Mutable Ramps. Factor in another £300 - £500 in supporting modules to get the most out of it.