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7.1. Keys, Modes, and Parent Keys

A key label combines a tonic root with a mode. Benchmark-Guided Modal currently uses Ionian, Dorian, Phrygian, Lydian, Mixolydian, and Aeolian. Locrian completes the traditional seven-mode pattern, but it is not part of detector-dependent planning in the initial release.

Each modal key can also be viewed through its parent Ionian pitch collection. Two modal keys may share a parent collection while emphasizing different tonics, or preserve one modal tonic while moving between parent collections. This is why one major/minor or Camelot-style label cannot describe every relationship Harmonic DJ can express.

The guide below holds the pitch collection fixed to C major’s white keys and moves only the tonic. Start on the highlighted key, continue across the white keys, wrap at C when needed, and stop when the tonic returns an octave higher: C to C is Ionian, D to D is Dorian, and so on.

Ionian1st mode · starts on C
Ionian uses the white keys of C major and starts on C C D E F G A B C
Dorian2nd mode · starts on D
Dorian uses the white keys of C major and starts on D C D E F G A B C
Phrygian3rd mode · starts on E
Phrygian uses the white keys of C major and starts on E C D E F G A B C
Lydian4th mode · starts on F
Lydian uses the white keys of C major and starts on F C D E F G A B C
Mixolydian5th mode · starts on G
Mixolydian uses the white keys of C major and starts on G C D E F G A B C
Aeolian6th mode · starts on A
Aeolian uses the white keys of C major and starts on A C D E F G A B C
Locrian7th mode · starts on BTheory only
Locrian uses the white keys of C major and starts on B C D E F G A B C

The circle of fifths in Gem Finder shows parent keys because it gives us a stable way to explore pitch collections while separately choosing the destination mode and modal tonic.