Harmony and Scales Trainer

A scale is a set of notes (typically seven, though pentatonic scales use five) chosen from the twelve available pitches. If you build a three-note chord — a triad — on each of those notes using only notes from the scale, you get the diatonic chords of that scale.

Each chord gets a Roman numeral based on its position in the scale. Uppercase numerals (I, IV, V) mean a major chord; lowercase (ii, iii, vi) mean minor; the little circle (viiº) means diminished; the plus (III+) means augmented. In a major scale the pattern is always: I ii iii IV V vi viiº. Other scales and modes produce different patterns — and that's why each mode has its own emotional flavor.

Pentatonic scales are a special case. Because they only have five notes, stacking thirds on each degree produces some chords that aren't conventional triads — you'll see suspended (sus2/sus4) and quartal voicings instead. Pentatonics are really melodic scales, not harmonic ones. Use the view toggle in the Reference panel to switch between two ways of looking at pentatonic harmony.

The dashed-outline button at the end of each row is the octave — the same chord as I, played one octave higher, so you can hear the full scale-root-to-scale-root sweep.

Click any chord below to hear it. Use the Quiz section to test whether you can identify which Roman numeral was just played.

Below the main app, you'll find a Sounds You'll Meet Later section — five additional scales you can hear but that aren't yet fully analyzed. Click any of them to listen. The full diatonic-harmony treatment for those scales will arrive in future releases.

This app is designed to be usable through audio alone. The Reference panel, the Quiz, and the Sounds You'll Meet Later section all play piano samples through your speakers — you don't need to see the chord grid to use them, as long as you can hear and operate the controls.

Every interactive control on the page has a screen-reader label that announces its meaning. Chord buttons announce both their chord symbol (like "C major" or "D minor") and their Roman numeral position (like "one major" or "two minor"). Roman-numeral analysis is a core teaching aim of this app, and the spoken labels are designed to make that learning accessible.

Keyboard shortcuts: single-letter keys (R, S, A, L, U, D, B) are wired to playback actions but may conflict with your screen reader's navigation. Switch your screen reader to focus mode while practicing. Tab navigation works throughout regardless of focus mode.

Companion apps: Ear Trainer trains interval and chord recognition purely by ear (no visual element required), and Music Reading Trainer trains visual recognition of music on the staff (which is necessarily sight-based). Together the three apps cover different musicianship skills approached from different senses.