Keyboardion
psst, hey kid, wanna read a weird programming book
July 27, 2026
Keyboardion
I had another idea for a musical instrument, and I think it worked out pretty well.
It’s sort of a cross between a chromatic button accordion and a keytar. Or maybe it’s a digital Chapman Stick… except that it’s more polyphonic and tuned completely differently.
I don’t know. It’s kind of a new thing, I think.
The chromatic button accordion is probably the oldest and certainly the most popular isomorphic keyboard instrument in the world, so it’s not that much of a new thing. But as far as I know, the keyboardion is the first instrument that adapts its tuning to this particular form factor.1
All of the digital isomorphic keyboards that I know about have more of a square aspect ratio,2 and they’re usually designed to be played like a piano or a concertina: both hands symmetrically engaged with the keyboard.
But I was really curious how this asymmetry would feel: the left hand probably plays in the bass register, so it can accompany the melody with chords. The left hand is pretty good at forming chords on a guitar. Maybe it’ll work on this weird keytar thing? Let’s find out.
Okay so what is this
The note layout looks like this:
A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯<br>I’ve highlighted a single full octave. Why did I highlight an octave starting at C♯? I dunno; that’s kind of just where I happened to draw this. You can slide that anywhere left or right; you could transpose this so that C is on the top row without changing the relative layout.
The important thing to note are the intervals: moving down and to the right goes up a semitone. Moving up and to the right goes up a whole tone. Moving directly to the right goes up a minor third.
This matches a “B-system” accordion, which the internet tells me is common in Russia. It also says that most Western chromatic button accordions use the “C-system” layout, which is the same thing but flipped upside down:<br>A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯<br>No idea if that’s true. I tried both, and found the intervals on the B-system more comfortable for common chord shapes on the left hand. For example, here’s the shape of a major triad in each system:<br>A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯<br>The left-hand shapes just felt more familiar and more guitar-like, I guess (remember, the left hand is coming from the “top” of this diagram). It’s easier for me to curl the index finger and extend the others than the other way around.
I’m not sure that this is the right decision – especially if you already play a C-system accordion – but that’s an easy thing to tweak.
Anyway.
What I’ve shown here – and built – is a three-row treble keyboard. That’s the minimum number of rows you need in order to span a whole octave, but it’s definitely not the ideal number of rows. As soon as I built this I started pining for a larger keyboard.
Like, I said this was the “shape” of a major triad:<br>A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯<br>Which is true if your root note is on one of the two upper rows. But what about C major? We can’t “go down a row” to find the third and the fifth, so we actually need to use a different chord shape for the exact same voicing:<br>A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯<br>And that particular shape is a lot less comfortable for my left hand.
This means that we’re missing one of the core benefits of an isomorphic keyboard layout: we can’t translate all of our chord shapes and intervals around the keyboard to any root note.
But there’s an easy fix: make the keyboard bigger, and continue the pattern of half steps and whole steps.<br>A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯C♯EGA♯C♯E<br>Notice that these new keys are redundant: the notes on the bottom row are exactly the same as the notes on the top row, just shifted over one.
This works for your basic triads, but we don’t have all possible chord shapes for all notes yet. A maj7 chord spans all three rows of the “base” layout; if we want to use the same shape for every root note, we need to add one final row:<br>A♯C♯EGA♯C♯BDFG♯BDCD♯F♯ACD♯C♯EGA♯C♯EDFG♯BDF<br>When you’re making an accordion, the redundant buttons are physically linked together – pressing one button will depress the corresponding redundant button, and they activate the same reeds, so adding rows doesn’t add too much complexity to the instrument. Some accordions even have six rows, so that each key has a redundant counterpart. This isn’t necessary to get isomorphic shape coverage, but I can imagine the additional fingering options are useful at the level of professional performance. I don’t know. I don’t play any of these instruments.
In any case, I built the simplest possible version: a three row keyboard. And I am just quietly sad when I have to switch between chord...