Key Signature Accidental Count Lookup

Resolve conventionally spelled major/natural-minor key signatures and ordered actual accidentals, distinguishing enharmonic keys and rejecting signatures beyond seven; not circle-of-fifths pitch-class position.

Description

A key signature is tied to spelled tonic and major/natural-minor mode.

A key signature is tied to spelled tonic and major/natural-minor mode. Enharmonic keys can carry different accidental counts.^[1]

Enter pitch-class tonic and exact major/minor. Require count within −7…7; return signed count, sharp/flat/none kind and accidentals in conventional order.

When to use Key Signature Accidental Count Lookup

Use Key Signature Accidental Count Lookup when you need to evaluate the supplied records under the calculation and evidence rules below. No signatures beyond seven or harmonic/melodic-minor inflections are supplied.

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

How to use Key Signature Accidental Count Lookup 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 tonic, mode using the field table and calculation rules, then run the tool.
Read signedSignatureAccidentalCount, signatureKind, orderedSignatureAccidentals. 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
tonic	Tonic	string	Required
mode	Mode	string	Required

Enter pitch-class tonic and exact major/minor. Require count within −7…7; return signed count, sharp/flat/none kind and accidentals in conventional order.

count=naturalTonicFifths+7×accidental−3 if minor

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

Output field	Meaning	Value type
signedSignatureAccidentalCount	Signed signature accidental count	number
signatureKind	Signature kind	string
orderedSignatureAccidentals	Ordered signature accidentals	list of string

json

{
  "input": {
    "tonic": "F#",
    "mode": "major"
  },
  "output": {
    "signedSignatureAccidentalCount": 6,
    "signatureKind": "sharp",
    "orderedSignatureAccidentals": [
      "F#",
      "C#",
      "G#",
      "D#",
      "A#",
      "E#"
    ]
  }
}

Limitations and assumptions

No signatures beyond seven or harmonic/melodic-minor inflections are supplied.

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.

Alternative or Complementary methods

Use Relative Minor Key Finder: A relative natural minor shares the major key’s signature while using its sixth degree as tonic. Correct spelling preserves that relationship. For a complementary task, use Parallel Key Lookup: Parallel keys retain the same spelled tonic while changing major/natural-minor mode. Their signatures differ from relative-key signatures.

References

Key Signature Accidental Count Lookup — tool.io

Similar or alternative tools

Relative Minor Key Finder
A relative natural minor shares the major key’s signature while using its sixth degree as tonic. Correct spelling preserves that relationship.
Parallel Key Lookup
Parallel keys retain the same spelled tonic while changing major/natural-minor mode. Their signatures differ from relative-key signatures.