What Is Jet Holt's Role in Designing and Programming Synth Modules?

Jet Holt co-designs and programs synthesiser modules in collaboration with Frequency Central, writing firmware in assembly for PIC microcontrollers. His role spans the full arc of a module's development: concept, circuit and firmware design, and prototype iteration. The work began with his first module at age 17 and now covers sequencers, logic tools, drum machines, and modulation sources.

The technical role: co-design plus assembly firmware

Holt describes the collaboration as programming and co-designing modules with Frequency Central. The core of his contribution is firmware: he uses PIC microcontrollers and writes in assembly code — a choice he notes gets him called a "troglodyte," a self-deprecating nod to how low-level the work is.

That combination matters for anyone trying to understand the modules. Assembly on a PIC means tight control over timing and I/O, which is exactly what sequencers and trigger generators depend on. It also means the behaviour of each module is defined in firmware as much as in hardware.

The modules, in order of development

Bartos Flur

The first module Holt ever programmed, built at 17 for his A-level Electronics course. Its defining quirk: the sequencer's step is set by the input voltage level rather than a conventional clock. Holt calls it "weird... but fun, too."

Deep Thought

Born from a joke — Holt was explaining logic gates to a teacher and suggested building a circuit with gates, switches, and LEDs as a learning tool. The result packs all the logic gates plus a flexible section that can behave as any gate. The name is a Hitchhiker's Guide reference, and Holt's own line is that hopefully it won't take 7,500,000 years to produce answers.

Polygraf

An accidental discovery: an experiment produced a powerful sequencer that "normal people" would struggle with, since reading binary was effectively required. Adding seven-segment displays and a reworked record mode turned it into a drum sequencer described as "like something Roland would have created in 1978."

Chronograf

Designed as a controller for Polygraf and similar modules — telling them when to go, when to stop, and which sequences to play. Holt's favourite feature is the wide variety of waveforms it produces, making it a strong modulation source.

What this tells you about the design approach

Two patterns run through the catalogue. First, constraints become features: binary step entry, voltage-determined sequencing, and all-gates-in-one-panel designs are all cases where a limitation or a joke turned into the module's identity. Second, modules are built as a system — Chronograf exists specifically to control Polygraf, so the range is meant to work together rather than as isolated units.

If you want to see the modules themselves, Holt's site links each one to its Frequency Central page, alongside development dates and demo videos credited to Frequency Central.