Function keySignatureFifths

keySignatureFifths(tonic: NoteLike, key: KeyLike): number
The key signature of a key, as a signed count of sharps (positive) or flats (negative) — the fifths value a notation format such as MusicXML writes.

The tonic's letter and accidental place the key on the circle of fifths, and the mode moves it from there: lydian +1, major 0, mixolydian -1, dorian -2, natural minor -3, phrygian -4, locrian -5.

A scale that is not a diatonic mode has no signature of its own, so it takes the signature of its parallel major or minor: a scale with a minor third and no major third counts as minor (-3), everything else as major (0). This is why A harmonic minor reports 0 — its G# is written as an accidental, not in the signature — and why A melodic minor reports 0 as well.

The result is not clamped: a theoretical key such as Fb major reports -8. Clamp to ±7 if the consuming format cannot express more.
Parameters
- tonic: NoteLike
  The spelled tonic, as a note name, note data, or a Note; its accidental is worth seven fifths.
- key: KeyLike
  The key/scale. This one stays a plain key/scale: it reads any 12-bit mask, including the tonic-less ones a key name cannot describe.
Returns number
The signed number of sharps (positive) or flats (negative).
Example
```
import { keySignatureFifths, majorKey, minorKey, parseNote } from '@libraz/libcantus';
keySignatureFifths(parseNote('Bb'), majorKey(10)); // -2
keySignatureFifths('A', minorKey(9)); // 0
```
- Defined in src/theory/scale/signature.ts:143

Function keySignatureFifths

Parameters

Returns number

Example

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