Writing by chord is an old idea. A stenographer presses several keys at once, and one stroke writes a whole word or part of one. It is fast, and it is hard to learn, because each system asks you to memorise thousands of outlines. Thorn keeps the chord and drops the memorising.
One finger, one place
The little finger is the hiss: S, Z and SH. The ring finger is the back of the tongue: K, G and NG. The middle finger is the lips: P, B and M. The index finger is the tip of the tongue: T, D and N. Press both keys of a finger and you get the related nasal.
Top is voiceless, bottom is voiced
Put a finger on your throat and say s, then z. The z buzzes. On the board t sits over d, p over b and k over g. Learn one key and its neighbour comes free.
Work it out
Four thumb keys write the vowels, alone or in groups. You can work out most chords from the sounds, instead of learning them by rote. If you can say a word slowly, you can write it.
What is in the app
Write
A page on top and the board underneath. Turn the phone sideways, press a chord, and the word appears. The keys can lean to follow the angle of your fingers.
My words
Add names and rare words with your own spelling. Your words win over the shared list, and they follow you between your devices through iCloud.
Reference
Look up any word and see its chord. Tap a row and the keys light on the board.
Words or sounds
Show ordinary spelling, or switch to sound spelling to see exactly what you pressed.
Alike-sounding words
To, two and too share a chord. Press one key straight after the word to change the spelling.
A keyboard works too
Use a Bluetooth keyboard if you prefer. One that reports many keys at once works best.
Young, and honest about it
Thorn is a new system, so three things are worth knowing before you start.
The word list is growing. A word that is not in the list appears as its sounds, so Dave might show as dayv. You can add words of your own.
It follows a southern British accent. The list spells words as a southern British speaker says them. If you say a word differently, Reference shows the chord the list expects.
Speed comes later. The first lessons are slow on purpose. Each chord should stop needing thought before you try to go faster.
There is a book
A short course goes with the app: ten chapters, each one sitting of about ten to fifteen minutes, with a pass mark so you know when to move on. It is still being written.