Three moments
Music theory you can see and hear, on the phone you already carry.
Temperament is a music-theory app built on a piano keyboard. Tap a key on the circle of fifths and its scale lights up below. Set a home note and its seven chords build themselves. Every screen makes sound, and nothing on it is decoration: if a key lights up, it is telling you something specific. I made it because I wanted my students to see the architecture rather than memorize it.
It is also the piece of work I would hand a skeptic first. It is real software, in daily use, with my name on it, and I am a singer, not an engineer. The second half of this page is about that.
This is the live app, the same one a student opens on a phone. Tap Begin, then tap a key on the wheel. Turn your sound up; the keyboard plays. Wander through the tabs along the top: chords, modes, ear training, the jazz lessons, the mathematics of why a fifth sounds the way it does.
A phone-sized frame on a laptop is a fair preview and nothing more. It was designed for one hand and a small bright screen, so if you want the real experience, open it full size on your phone and add it to your home screen. It works there with no connection at all.
Open Temperament full sizeThe piano keyboard is the through-line. Intervals become distance, chords become shape, scales become paths, and the circle of fifths becomes a map. The same one-octave keyboard appears wherever a concept can be shown on it, and it always speaks the same language: red for the root, copper for a chord tone, a quiet dot for a note that belongs to the key. Learn the grammar once and every room reads the same way.
The key signatures mapped as a wheel, so harmonic distance and visual distance are the same distance.
FreeSet a tonic, watch the seven diatonic chords build, hear each one on the keyboard, inversions and all.
FreeThe same seven notes, seen from a moving home. Hear each mode and see its shape.
FreeExplore the intervals by ear on the keyboard, then test yourself against them and against chord quality.
Explore free · challenge in the full appEleven lessons in order, from guide tones and the ii–V–I to altered dominants, rhythm changes, and reharmonization.
Three free · eleven in the full appThe acoustics under the theory. Every ratio plays in pure just intonation, so you can hear why equal temperament is a compromise.
FreeHow the system got built, and by whom, from the ancient world to the modern one. Checked against current scholarship.
Free122 questions across five topics, mixed so no subject clusters. Every answer explains the why rather than marking it right.
Ten free · all in the full appAdd it to your home screen and it opens full screen, no browser bar, and works with no connection. No account, no ads, no cookies.
Free, alwaysI am a singer by training. I am not a software engineer. For most of my working life the distance between what I could imagine and what I could actually build was the defining frustration of my days, and Temperament is what happened when that distance closed.
I designed it, wrote the teaching, and argued every theory question in it. The code was written by an AI under my direction, one change at a time, from a first sketch in June 2026 through more than two dozen builds since. My job at each step was the one I know from the rehearsal room: decide what is true, decide what is worth the audience's time, and refuse anything that sounds confident and isn't. When a chord lit the wrong key, I heard it. When a history panel repeated a legend as fact, it got rewritten to say what the scholarship says. Every quotation in the app has been traced to its source; two that couldn't be were replaced with ones that could.
The engineering held to the same rule. The whole app is one file. It runs in any browser, installs to a phone, and works with the network off. Nothing was declared finished on the strength of reading the code; it was run, on a phone-sized screen, and looked at. That habit caught more than one bug that a code check had passed.
I use artificial intelligence the way any craftsman uses a fine tool: the result depends entirely on the hand directing it. What I deliver is shaped at every step by my standards, my judgment, and my responsibility for the outcome. I’m transparent about the method because transparency is what makes the work trustworthy, and I put my name on it because I stand behind it.
Temperament was built first for the young, serious musician: the undergraduate music student and the jazz student who need a sharper reference and a fresher framing than the textbook gives. Curious amateurs and lifelong music lovers are welcome in the same room, and most of the app is free to all of them.
Everything free stays free. The full app opens every jazz lesson, the ear-training challenges, and the whole quiz, on every device you own. Paid once. No subscription.
One link for a whole class, no student accounts and no student data, a syllabus map to the standard first-year sequence, and a term that ends with the academic year. Details and a sell sheet on request.
Made with AI as a tool, under my direction and judgment at every step. I stand behind this work as fully as anything I've made by hand.
Matthew Curran, Curran Crafts