Neapolitan ♭II Chord Identifier

Identify spelled lowered-second major triad and separately observed traditional first inversion; does not require inversion for chord identity or claim chromatic pitch-class similarity proves Neapolitan function.

Description

A Neapolitan triad uses the spelled lowered second as a major root.

A Neapolitan triad uses the spelled lowered second as a major root. Its common first inversion is separate evidence from chord identity.^[1]

Enter pitch-class major tonic, observed root/quality and bass. Validate supported explicit quality, then return Neapolitan identity and first-inversion flag gated by identity.

When to use Neapolitan ♭II Chord Identifier

Use Neapolitan ♭II Chord Identifier when you need to evaluate the supplied records under the calculation and evidence rules below. Root position can still match the triad. Enharmonic class alone does not establish spelling or harmonic function.

Enter the written notes, explicit grouping, pitch observations or supported chord tokens requested. Keep scientific octaves, accidentals and caller evidence consistent.

How to use Neapolitan ♭II Chord Identifier and understand its results

Enter the written notes, explicit grouping, pitch observations or supported chord tokens requested. Keep scientific octaves, accidentals and caller evidence consistent.
Enter majorTonic, observedChordRoot, observedChordQuality, observedBassNote using the field table and calculation rules, then run the tool.
Read matchesNeapolitanMajorTriad, firstInversionObserved. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
majorTonic	Major tonic	string	Required
observedChordRoot	Observed chord root	string	Required
observedChordQuality	Observed chord quality	string	Required
observedBassNote	Observed bass note	string	Required

Enter pitch-class major tonic, observed root/quality and bass. Validate supported explicit quality, then return Neapolitan identity and first-inversion flag gated by identity.

match=degree2 AND alteration−1 AND major; inversion=bass is spelled major third

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
matchesNeapolitanMajorTriad	Matches neapolitan major triad	boolean
firstInversionObserved	First inversion observed	boolean

json

{
  "input": {
    "majorTonic": "C",
    "observedChordRoot": "Db",
    "observedChordQuality": "major",
    "observedBassNote": "F"
  },
  "output": {
    "matchesNeapolitanMajorTriad": true,
    "firstInversionObserved": true
  }
}

Limitations and assumptions

Root position can still match the triad. Enharmonic class alone does not establish spelling or harmonic function.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Borrowed ♭VII (Mixolydian) Check: A borrowed flat-seven major chord is spelled on the lowered seventh of a major tonic. Enharmonic equality alone loses that degree evidence. For a complementary task, use Chord Inversion From Bass Note: Inversion identifies which spelled chord member is the supplied actual bass. A nonchord bass should remain visible rather than forced into an inversion.

References

Neapolitan ♭II Chord Identifier — tool.io

Similar or alternative tools

Borrowed ♭VII (Mixolydian) Check
A borrowed flat-seven major chord is spelled on the lowered seventh of a major tonic. Enharmonic equality alone loses that degree evidence.
Chord Inversion From Bass Note
Inversion identifies which spelled chord member is the supplied actual bass. A nonchord bass should remain visible rather than forced into an inversion.