Analyze a chord in the context of a given key:

analyze (Chord.minor PitchClass.e) Key.c == iii


analyze (Chord.major PitchClass.a) Key.c == vOfii

Convert to a chord in the specified key:

toChord triadsByDefault Key.f iii == Chord.minor PitchClass.a

Use triads when converting, if no chord type is specified:

toChord triadsByDefault Key.f iv == Chord.major PitchClass.bFlat

Triads are the default for harmonizing the scale in classical music.

Use seventh chords when converting, if no chord type is specified:

toChord seventhsByDefault Key.f iv == Chord.majorSeventh PitchClass.bFlat

Seventh chords are the default for harmonizing the scale in jazz music.

Get the symbol for a Roman numeral analysis:

toString Key.c iv == "IV"


toString Key.cMinor iv == "iv"


toString Key.c (viiFlat ChordType.majorSeventh) == "♭VIIM7"

The Key parameter is used to determine whether to render the symbol in the context of a major or minor key.

Diatonic scale degrees have default chords types in major or minor scales. This function lets you use others:

iii
    |> withChordType ChordType.majorSeventh
    |> toString -- "IIImaj7"