Over the last year I have been learning both ukulele and mandolin, after 20 years of playing guitar. As I tweeted over the weekend, I bought a ukulele and looked for a chord app. I had a couple for guitar, but none of them supported ukulele. I found out pretty quickly that most of the apps suffered from similar issues. They were hard to use— bad UX/UI—, lacked iOS esthetic, and didn’t have the features I needed most where they needed to be.
Now so much of that is subjective. Yes. True. When I am looking for a chord voicing, I am looking for where I can play it. The most popular apps show a single voicing at a time.

Take this app from The Ukulele Teacher. Are there other voicings? I will guess that the 1/32 up top indicates that there are. But how do I get to them. Swipe right to left? Nope. Maybe that next arrow in the bottom right? Crap! Now it’s playing an audio clip of the voicing. Swipe up? There it is! But no scroll indicators, just a change of the fretted notes and the “1/32” changed to “2/32”.
Now I want to switch to a D minor. How do I do it? Tap the C major “title” up top? No. The music note at the bottom?

Not the easiest thing to use. And to be hidden away behind an ambiguous button when it is an action I am going to use the most? Not good.
Pulling Back
I have been playing guitar for 20 years and never learned basic music theory. I didn’t know how chords were formed, just where they were. Sure, I knew that they were multiple notes being played, but I never cared or concerned myself with which notes aside from my root was being played.
So I started there. How is a C major chord formed? Well, it’s based on the C major scale. I didn’t know my scales. Or how they were formed. Guess I would start there.
A scale starts with the root note and then takes a certain number of whole and half steps between notes back around. A major scale, for instance goes 1, 1, 0.5, 1, 1, 1, 0.5. That C major scale? C, D, E, F, G, A, B, C.
So back to that C major chord. How is that chord formed? A chord is formed on intervals of a scale. The major chord is using the I, III, and V intervals of major scale. Roman numerals for some reason. There is likely a wiki page for that explanation, if you are interested. So we start at I, which is our C, go to III, our E, and end on V, our G.
To the programmer reading this, you might have noticed that this is math. I certainly did. And math I can do. I love math.
So I Built an App
Looking through the App Store for an app that scratched my itch made me sad. As a UX/UI engineer, I decided that if this was just math, I could design a better looking/working app and build a chord finder that didn’t suck. But first I needed an engine. Take that math and turn it into an algorithm. An algorithm that I could hand a set of strings and tell it to find the C major voicings— different ways to play it across the neck of my ukulele.
This was, surprisingly, done on an iPad. I opened Swift Playgrounds and built the first prototype of the algo there. Even had it doing basic drawing of the chord chart.
The algo was straight-forward. Use the above math to find the notes of the requested chord, find all the notes on the set of strings given, then find all possible combinations of those notes on those strings. From there start narrowing it down to actual, playable chords.
It worked, so I started the design process.
Defining the App
What’s in and what’s out. So I had a powerful algorithm. I could give it 4 strings, and it’d find the voicings of a specific chord. I could give it 5 strings. Six strings. Seven. Ooo. I decided I wanted to support multiple instruments, obviously guitar and ukulele being the top of that list. But as I built the first working prototype app and had it running on my phone, I switched to mandolin strings and went to Guitar Center to play around. See how well it worked and if I could pick up another new instrument. And it was a success. One that went onto me buying a mandolin too.
The app was to stay simple. Prize simplicity, be willing to hold back functionality that other apps may have. No scales, no arpeggios, lots of noes.
So what was required?
A beautiful, clean interface. Easily scroll through a list of chord voicings. Big enough that you could read them comfortably, but small enough that you could see many at once.

A simple mechanic to switching between chords. That above ukulele app made it very difficult to switch chords. Others do as well. I wanted none of that. So my app would have two bars. Segmented controls. Easily switch between root notes and chords.

Multiple instruments/tunings and easy switching between them. This would be in a drop down. I wanted this to be quick to access, but you wouldn’t be switching instruments as often as you switched chords, so a drop down was logical.

Removing Features and Narrowing in on Version One
I wanted banjo support in version one. And the ability to mark a voicing as a favorite. And support for adding custom tunings. But shipping is more important. I shifted from feature building to spit-shine mode in October, realizing that I had a perfectly usable app.
I always remind myself of 37signals’s Rework book. Do I want a half-assed whole product or a kick-ass half product? I can ship a dozen features with bugs and no polish or ship a half-dozen features with delight and polish galore.
So I Spent My Year on an App
Like most programmers that decide to pick up a new hobby, instead of learning and mastering ukulele this year, I learned basic music theory, built, and launched an app.
Yeah.
Selah Chords has shipped. And the initial reviews are that it is beautiful, intuitive, easy-to-use, and extremely useful.
And coming soon, banjo and favorite voicings. And after that, custom tunings.
Get it for free today!