GREAT CONJUNCTION: Generative FM Sequencer with Yamaha YM2413 Chip

November 23, 2025 by Little Music

GREAT CONJUNCTION from Distropolis Goods is not your typical sequencer. Instead of placing notes manually, this device generates music algorithmically, creating evolving patterns that shift and transform over time. At its heart is a vintage Yamaha YM2413 FM sound chip, the same chip found in 1980s keyboards and game consoles.

Three Sequencers, One Voice

The device features three independent generative sequencers, each capable of 1 to 32 steps. These sequencers can run at different speeds and lengths, creating polyrhythmic patterns that constantly shift in relation to each other. What makes GREAT CONJUNCTION unique is how these sequencers interact with the sound engine.

All three sequencers send their instructions to a single custom FM instrument. When multiple sequencers try to control the same voice simultaneously, their conflicting data creates what Distropolis Goods calls "conjunctions" - unexpected timbral shifts and FM artifacts that would be difficult to program intentionally.

GREAT CONJUNCTION generative FM sequencer

Algorithmic Generation Methods

Each sequencer can use one of three generation methods:

Pseudo-random sequences create chaotic, unpredictable patterns. The event density controls the probability of notes occurring, while a random seed parameter determines the initial pattern. Set the seed to random mode, and the pattern redistributes itself on each cycle.

Euclidean sequences distribute events evenly across the available steps. The algorithm creates rhythmically interesting patterns, especially when the number of events doesn't divide evenly into the number of steps. This method often produces recognizable grooves and polyrhythmic structures.

Cellular automata sequences evolve continuously according to mathematical rules. The initial pattern is set randomly, but from that point forward, each step influences its neighbors according to the selected rule. Different rules create vastly different evolution patterns, from quickly dying sequences to continuously generating variations.

Full FM Control

Beyond the sequencing capabilities, GREAT CONJUNCTION provides complete control over the YM2413 FM parameters. The two-operator FM engine includes separate ADSR envelopes for both the modulator and carrier, frequency multipliers, waveform selection, and feedback control.

The device includes 100 preset instrument sounds, split between percussion and melodic tones. Users can assign different custom instruments to each of the three sequencers, creating additional sonic possibilities when these instruments conflict during playback.

Evolution and Transformation

Each sequencer parameter can evolve over time. Set an evolution percentage for any parameter - instrument type, step count, event density, root note, scale, or octave - and GREAT CONJUNCTION will randomly change that parameter based on the probability setting. This creates patterns that shift and transform organically during performance.

Interface and Connectivity

The front panel features 12 knobs and 5 buttons, with a 20×4 backlit LCD display showing the current sequence patterns and parameters. The semi-transparent 3D-printed enclosure comes in two variants: Dark Crystal and Light Crystal.

MIDI connectivity includes both USB and TRS-A jacks for input and output. The device can send and receive MIDI clock, transport messages, and note data. Each sequencer can be set to different MIDI channels, and there's a keyboard mode that turns GREAT CONJUNCTION into a playable 9-voice polyphonic FM synthesizer.

The device offers 10 save slots for storing complete setups, plus three randomize options: full randomize, harmonic randomize (which keeps all sequencers in the same scale), and hold randomize (which maintains the current root note and scale while randomizing other parameters).

Who Is This For?

GREAT CONJUNCTION appeals to musicians who enjoy working with generative systems and embracing unpredictability in their creative process. If you find yourself drawn to modular synthesis, algorithmic composition, or experimental electronic music, this device offers a different approach to sound generation.

The lo-fi character of the YM2413 chip gives the device a nostalgic, retro gaming aesthetic that works well for chiptune producers and anyone interested in vintage digital sounds. The FM synthesis engine can produce everything from bell-like tones to harsh, metallic textures that sit somewhere between classic 8-bit game music and modern experimental electronics.

Ambient and drone musicians will appreciate how the evolution parameters create slowly shifting soundscapes without manual intervention. Set up a pattern, adjust the evolution settings, and let the device generate hours of continuously transforming material.

Musical Applications

The polyrhythmic capabilities make GREAT CONJUNCTION useful for creating complex rhythmic beds. Euclidean sequencing naturally produces patterns that work well for techno, IDM, and other electronic dance music styles. The ability to run three different subdivisions simultaneously creates interesting metric modulations and polyrhythmic textures.

For experimental and noise music, the collision of conflicting sequencer data produces glitchy, unstable timbres. Push the FM parameters into extreme ranges, set high evolution percentages, and let the three sequencers fight for control of the sound engine.

The cellular automata mode works particularly well for generative ambient pieces. Different rules create different evolution patterns - some settle into stable loops, while others continuously generate new variations. Combined with the scale quantization and evolution parameters, you can create melodic material that stays harmonically consistent while evolving unpredictably.

Hip-hop and beat makers might use GREAT CONJUNCTION as a source for unusual percussion sounds and melodic fragments. The YM2413 chip excels at bell tones, metallic hits, and bass sounds that can add character to sample-based productions.

Integration and Jamming

GREAT CONJUNCTION works well as both a standalone instrument and as part of a larger setup. The MIDI output makes it useful as a generative sequencer for controlling external synthesizers. Send each of the three sequencers to different synths on different MIDI channels, and you have a polyrhythmic, polyphonic composition system.

Sync it to your DAW or hardware sequencer via MIDI clock, and GREAT CONJUNCTION becomes a source of rhythmic and melodic variation within a larger arrangement. The transport controls allow it to start and stop in time with other gear.

The compact size makes it ideal for desktop setups alongside other small synthesizers like Pocket Operators, Volcas, or Bastl instruments. The mono audio output can go directly into a mixer, effects pedal chain, or audio interface.

For live performance, the hands-on interface allows real-time manipulation of all parameters. Adjust evolution settings during a performance to make patterns more or less chaotic, change scales to shift the harmonic content, or switch between generation methods to create structural changes.

Pairing GREAT CONJUNCTION with effects processors extends its sonic palette significantly. Reverb and delay emphasize the melodic patterns and create space around the lo-fi FM sounds. Distortion and saturation can push the already aggressive FM timbres into harsh noise territory. Granular effects can transform the rhythmic patterns into textural clouds.