Chord Organ module on a desk, cable atached.

Getting chords out of a modular synthesizer is not fun. At least not for me. Maybe it is for people with more skill or bigger systems or a stronger masochistic streak in them than I got. But for me, it’s close to impossible. I have a Plaits which can do chords, but I like and use it for other reasons.

What I really like and what gives me a warm feeling is the sound of (maybe a bit jazzy) chords consisting of a bunch of simple sign waves. Not a difficult thing to do on your favorite polysynth, but as I said, not fun on a modular. And when I saw the Chord Organ by Music Thing Modular do it in the easiest way ever, I wanted one.

About the Chord Organ?

The Chord Organ is an alternative firmware of another eurorack module by Music Thing Modular respectively Tom Whitwell, the Radio Music, kind of a sampling radio thingy. The heart of the module is a teensy microcontroller which can be freely programmed. So, the module can be seen as a more or less simple platform for all kinds of possible eurorack modules.

The Chord Organ plays chords. The root note of the chord is defined by a CV input and a knob. The same counts for the chord shapes. Up to 16 shapes can be defined in a configuration file (CHORDORG.TXT) and be selected via another CV input and knob. In addition, it is possible to configure some more features in this file, like glide, note stacking and some more. Fot the fans of microtonal music it is also possible to create a separate tunig file (TUNING.SCL), to have the Chord Organ tuned in an alternative way.
That is roughly it.

Show me what a CHORDORG.TXT looks like!

This is what a CHORDORG.TXT looks like!


1  [0,4,7,12,0] Major
2  [0,3,7,12,0] Minor
3  [0,4,7,11,0] Major 7th
4  [0,3,7,10,0] Minor 7th
5  [0,4,7,11,14] Major 9th
6  [0,3,7,10,14] Minor 9th
7  [0,5,7,12,0] Suspended 4th
8  [0,7,12,0,7] Power 5th
9  [0,5,12,0,5] Power 4th
10 [0,4,7,8,0] Major 6th
11 [0,3,7,8,0] Minor 6th
12 [0,3,6,0,3] Diminished
13 [0,4,8,0,4] Augmented
14 [0,0,0,0,0] Root
15 [-12,-12,0,0,0] Sub Octave
16 [-12,0,0,12,24] 2 up 1 down octaves

The modifications: Chord Organ Chamäleon

So, I got my kit from the UK (Did I ever mention what a pain in the ass this brexit clusterfuck is? I will never get over it…), built it and played around with it. It is great. I love it! <3

What seemed a bit unnecessary to me was whenever I wanted a different behavior of the module, I had to remove the SD card, go to my computer, make changes to the config file and then go back to my modular to re-insert the SD card and reload. So, I wanted to change this (and maybe because the feature creep is strong in me).

With my modified version of the Chord Organ firmware it is possible to have up to ten different config files on the SD card. They would be called: CHORDORG.TXT, CHORDORG1.TXT, CHORDORG2.TXTCHORDORG9.TXT Loading the next file is done by a long butten press (at least for one second). The number of blinks of the waveform LEDs indicate which file will be loaded.
The long button press was formerly reserved to toggle the stacked notes feature on and off. But since note-stacking is also configurable in the config file, this feature still exists, if wanted.

I also made the alternative tuning file configurable by using !TUNING <FILENAME>. A config file with an alternative tuning could look like this:

!TUNING 08-EDO.scl

1  [0,4,7,12,0] Major
2  [0,3,7,12,0] Minor

This way, it is possible to cycle through different tunings, if you want to.
I for my part have no clue about alternative tunings, so sorry for the bleeding ears in my little demo.

You can find the Chamäleon fork of the firmware repository here.
The current Chord Organ Chamäleon hex file can be downloaded here
. This one can be loaded to your module via the Teensy Loader Application directly.

Many thanks to Tom Whitwell and Martin Wood-Mitrovski for this fantastic device!
Have fun with your chords.

15 August 2021


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