Curran Crafts

A Curran Crafts original

Temperament

The Nature of Music

A music theory reference you can see, hear, and understand. Eight sections, one keyboard uniting them, and what you see is what you hear.

Most of it is free to explore, in any browser.
$29, once, unlocks the rest.

Open Temperament What’s inside

Start with a note. Tap Begin, then tap a key on the circle of fifths to hear its scale. Sound starts when you tap; on iPhone, turn silent mode off.

Made for one hand and a phone screen. On your phone, open it full size and add it to your home screen: it works with no connection. Open Temperament ↗

The keyboard connects the ideas.

Intervals become distances on the keyboard. Chords become shapes. Scales become paths through the notes.

  • Red is the root, or home.
  • Copper is a chord tone.
  • A quiet dot is a note in the key.

The keyboard here shows C major, with its tonic chord lit. The same keyboard appears wherever an idea can be shown on it, and it always speaks this language.

What’s inside

Eight sections,
one keyboard.

No account, no ads.

Temperament’s Circle of Fifths on a phone, with the key signatures around the wheel and the scale shown on the keyboard below Temperament’s Keys and Chords screen on a phone: the seven chords of C major above a keyboard with C7 lit, and the chord qualities to choose from Temperament’s Modes screen on a phone: Aeolian selected, its home note A lit on the keyboard, with its description as the natural minor scale Temperament’s Ear Training screen on a phone: Chord Quality set to sevenths, with C half-diminished lit on the keyboard and spelled C E♭ G♭ B♭ Temperament’s Tuning lesson “The gap” on a phone: twelve pure fifths drawn against seven octaves, overshooting by 23.46 cents, with a button to hear where each route ends Temperament’s first Jazz lesson, Guide Tones, on a phone: C major on the keyboard with the root in red, the 3rd as a guide tone and the 5th as scaffolding

  1. Circle of Fifths

    Free

    All twelve keys on one wheel, with their key signatures. Tap a key to hear its scale and see it on the keyboard.

  2. Keys & Chords

    Free

    Set a home note, major or minor, and its seven chords appear. Build any chord, then see and hear its inversions.

  3. The Modes

    Free

    The same seven notes, seen from a moving home. Hear each mode and see where it settles.

  4. Ear Training

    Free to explore

    Intervals, chord quality (triads and sevenths), and cadences. Learn each by ear, then test yourself. Ten Challenge rounds a month are free.

  5. Tuning

    Free

    Nine short lessons on why a piano is tuned the way it is, from pure ratios to equal temperament. Every ratio plays, so you can hear what the compromise costs.

  6. History

    Free

    How Western music theory was built, from Pythagoras onward, checked against current scholarship.

  7. Jazz

    First three free

    Twelve lessons in order: guide tones and chord-scales, the blues, secondary and altered dominants, modal interchange, rhythm changes, and reharmonization.

  8. Quiz

    Ten a month free

    143 questions across five topics. Every answer explains why, so a wrong guess teaches as much as a right one.

A keyboard that doesn’t lie.

E

Every scale on its own letters.

F♯ major ends on E♯, not F, because a scale uses each letter once. Chords are spelled up from their root, double sharps and all.

1:1

The black keys keep their proportions.

The black keys keep their true proportions, even where shrinking them would have made the layout easier.

660

Checked one by one.

Every chord the app can show was checked in every key and every inversion: 660 voicings, each lighting exactly the notes it plays.

The name

Why “Temperament”?

Nature gives us relationships.
We make a system.

Nature leaves a remainder. Twelve pure fifths overshoot seven octaves by a sliver, the way the solar year overshoots 365 days by a quarter. The calendar absorbs its remainder with a leap day. Temperament spreads its remainder across the twelve keys, so thin that no one hears the seam. No interval is quite pure. Every key is open. The Tuning section lets you hear exactly what the trade costs.

It is also a fair description of how anyone builds something that works from parts that don’t quite fit. You give up a little purity in each piece so the whole can move. The name is there to remember that the compromise was a choice, and that someone had to decide what it was worth.

Matthew Curran singing from a score in a church, in a dark suit
Matthew CurranProfessional singer in opera, concert, and song. Coach. AI Craftsman.MM, Indiana University · BM, Loyola University New Orleans

How it was made

A musician’s knowledge. New tools to give it form.

I’m a professional singer, not a software engineer. I brought my musical knowledge and teaching decisions to Temperament; artificial intelligence helped me turn them into working software.

My role was to direct the work, listen to what it produced, and check the musical details. That includes what a chord sounds like, which notes the keyboard shows, and how a concept is explained. It is the discipline of the rehearsal room: decide what is true, decide what is worth the audience’s time, and refuse anything that sounds confident and isn’t.

I’m open about the tools because they are part of how this was made. The judgment and responsibility for what I put my name on are mine.

If you want to make a first version of something yourself, .

Hold that thought for a coming offering from Curran Crafts.

For one musician

The full app

$29 one time

Everything free stays free. The full app adds the remaining nine Jazz lessons, unlimited Challenge rounds, and the whole 143-question Quiz. Your license key arrives by email and unlocks the full app on every device you own. No account, no subscription.

This is the first version. If people buy it, I’ll keep building it: more Challenge material, more lessons, and in time a standalone app. Buying now funds that, and whatever is added, you’ll already have it. If the app ever moves, I’ll send every owner a new key.

Buy on the Temperament site

For a studio, a department, a school

Classroom licenses

From $150 a year

One access link for a whole class, with nothing to install and no student accounts, plus a syllabus map pairing each section with the weeks of a standard theory sequence. Department and Institution licenses include a live session with me.

See classroom licenses

Founding programs: the first five departments to sign for the 2026 to 2027 year pay half, in exchange for a conversation at the end of each semester about what students used and what they ignored. Need an invoice, a purchase order, or a W-9? Write to me and I’ll handle it by hand.