Parallel Key Lookup
Resolve parallel major/natural-minor key with unchanged tonic spelling and both conventional signatures, preserving signed accidental change; not relative-key rotation.
Description
Parallel keys retain the same spelled tonic while changing major/natural-minor mode.
Parallel keys retain the same spelled tonic while changing major/natural-minor mode. Their signatures differ from relative-key signatures.1
Enter pitch-class tonic and exact major/minor source mode. Validate both conventional signatures within ±7; return opposite-mode label, both counts and signed change.
When to use Parallel Key Lookup
Use Parallel Key Lookup when you need to evaluate the supplied records under the calculation and evidence rules below. Some spelled tonics cannot support both bounded signatures and fail. No harmonic/melodic-minor alterations are modeled.
Enter the written notes, explicit grouping, pitch observations or supported chord tokens requested. Keep scientific octaves, accidentals and caller evidence consistent.
How to use Parallel Key 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, sourceMode using the field table and calculation rules, then run the tool.
- Read parallelKeyLabel, sourceSignatureAccidentalCount, parallelSignatureAccidentalCount, signedSignatureChange. 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 |
| sourceMode | Source mode | string | Required |
Enter pitch-class tonic and exact major/minor source mode. Validate both conventional signatures within ±7; return opposite-mode label, both counts and signed change.
signatureMinor=signatureMajor−3; change=target−source Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| parallelKeyLabel | Parallel key label | string |
| sourceSignatureAccidentalCount | Source signature accidental count | number |
| parallelSignatureAccidentalCount | Parallel signature accidental count | number |
| signedSignatureChange | Signed signature change | number |
{
"input": {
"tonic": "C",
"sourceMode": "major"
},
"output": {
"parallelKeyLabel": "C minor",
"sourceSignatureAccidentalCount": 0,
"parallelSignatureAccidentalCount": -3,
"signedSignatureChange": -3
}
}Limitations and assumptions
Some spelled tonics cannot support both bounded signatures and fail. No harmonic/melodic-minor alterations are modeled.
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 Key Signature Accidental Count Lookup: A key signature is tied to spelled tonic and major/natural-minor mode. Enharmonic keys can carry different accidental counts.
References
-
Parallel Key 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.
- Key Signature Accidental Count Lookup
A key signature is tied to spelled tonic and major/natural-minor mode. Enharmonic keys can carry different accidental counts.