Polyphonic: Using the Keystep Pro for 4-Voice Polyphony in Eurorack Modular - with AJH Synth MiniMod

video upload by AJH Synth Official

"This video demonstrates the Arturia Keystep Pro controlling a MiniMod system in polyphonic mode, and show's how to enable up to 4 voices of polyphony on the Keystep Pro controller keyboard. The MiniMod system uses just 4 VCO's, envelope generators, VCF's and VCA's to supply 4 simple, single-oscillator voices, which are then complimented by either an LFO or noise source to add interest to the sound. This really is about as spartan as you can get for a modular 4-voice setup, so adding further modules would greatly expand it's sound palette, but this is just a proof of concept. Since it's fully modular, even with such a simple voice structure a surprising range of sounds can be achieved.

This was partly inspired by the earliest polyphonic synths, which were initially huge modular systems controlled by polyphonic keyboard controllers, and then the first polyphonic Oberheim synths, which controlled 4 or 8 individual monophonic synth voice modules individually (the superb-sounding SEM), each needing to be setup and tuned. However, this meant that each voice was free to be whatever the user wanted - similar or completely different than the others, something conventional analogue polysynths can't do.

The Gemini 2412 is used here as it has extensive multi-mode filter options, and conveniently contains 2 fully-featured VCF's per module, but also since it is directly based on the filter from the classic SEM module. A pair of Contour Generators serves as a simple and convenient dual envelope per module, although here they are shared for both VCF and/or VCA.
It's unlikely that many would buy a complete modular system purely to use as a polyphonic synth, but as your system grows it may eventually provide sufficient modules to be used in a poly configuration, even just as 2 voices, such as here: [posted here]

POWER: This module setup and PSU is just an example of the concept - it isn't necessary to arrange the modules in this way, and you should always ensure your power supply is sufficient to provide significantly more power to your selection of modules than is needed, across the +12V, -12V, and 5V power lines. For example, in this setup I'm using roughly 400mA on the -12V rail, but the PSU only provides 500mA to -12V, so this is pushing it a little too close to the limit than is ideal. Modulargrid.net is a great tool to use for designing your system and calculating your power needs, but also consult your PSU's documentation for advice on power usage.

MODULES USED:
Vintage Transistor Core VCO x4
Gemini 2412 x2
Contour Generators x2
Discrete Cascaded VCA x4
Dual LFO + VCA x1 (optional)
Entropic Doom x1 (as a noise source, optional)
Precision Voltages (as an offset for Gemini D-FCV, optional)
V-Scale x1 (as a buffered multiple, optional)

The AJH SYNTH Eurorack range consists of high-end modules, all hand-made in the UK, most of which are based on classic, vintage designs, authentically recreating the circuitry of much sought-after analogue instruments and technologies of the past, whilst greatly expanding them, and bringing them to modern Eurorack levels of convenience, limitless flexibility, and reliability.

Check out the AJH Synth playlists for module 'User Guides', and 'Patch of The Week' videos, which will be either performances or 'how to' guides, detailing functions/methods, and a range of sounds, some familiar, some less so, containing a patch sheet at the end to show you how to construct it for yourself.

Video by @DreamsOfWires"