Name the pattern.
Type any chord progression. The analyzer detects the key, assigns Roman numerals, maps harmonic function, traces the tension flow, and measures voice leading distance. Paste a song's chords and see the structure underneath.
Uppercase = major. Lowercase = minor. The numeral shows which scale degree the chord is built on. I is home. V wants to go home. iv is borrowed sadness.
Tonic = stability. Dominant = tension that pulls toward tonic. Predominant = sets up the dominant. Chromatic = outside the key. Every chord has a role in the sentence.
The curve shows how tension rises and falls through the progression. Tonic is low. Dominant is high. Good progressions breathe — they build tension and release it.
Common tones are notes shared between consecutive chords. More common tones = smoother connection. Smooth voice leading means each note moves as little as possible.
The red exclamation mark means a chord is not diatonic — it does not belong to the key. This is not wrong. It is color. Modal mixture, secondary dominants, chromatic mediants. The interesting chords are usually the borrowed ones.
The analyzer guesses the key by scoring how well the chord tones fit each possible major and minor scale. You can override it if the guess is wrong — sometimes ambiguity is the point.
Analysis is not judgment. Calling a chord "borrowed" does not mean it is wrong. It means it came from somewhere else. The labels help you see the grammar. What you do with the grammar is yours.