MCC::Key Class Reference

A tonic and a diatonic mode, with the key signature they imply. More...

#include <Key.h>

Collaboration diagram for MCC::Key:

Public Member Functions
constexpr	Key () noexcept
	Creates the invalid key (SPEC-ERR-2).
constexpr	Key (NoteName tonic, KeyMode mode) noexcept
	Creates tonic in mode; invalid beyond seven sharps or flats.
constexpr bool	IsValid () const noexcept
	Returns true unless this is the invalid key.
constexpr NoteName	Tonic () const noexcept
	Returns the tonic.
constexpr KeyMode	Mode () const noexcept
	Returns the mode.
constexpr KeySignature	Signature () const noexcept
	Returns the key signature, or the invalid signature.
Scales::Id	ScaleId () const noexcept
	Returns the catalog scale of the mode, or Scales::Id::Invalid.
MCC::Scale	Scale () const noexcept
	Returns the key's scale spelled from its tonic.
MCC_CONSTEXPR14 NoteName	Spell (MCC::PitchClass pitchClass) const noexcept
	Writes pitchClass in this key's context (SPEC-KEY-3).
MCC_CONSTEXPR14 MCC::Pitch	Spell (MCC::ChromaticIndex index) const noexcept
	Writes a sounding chromatic index as a pitch in this key's context.

Static Public Member Functions
static MCC_CONSTEXPR14 Key	FromSignature (KeySignature signature, KeyMode mode) noexcept
	Returns the key with signature in mode (2 sharps + Minor = B minor).
static constexpr Key	Invalid () noexcept
	Returns the invalid key.

Friends
constexpr bool	operator== (const Key &a, const Key &b) noexcept
	Compares tonic spelling and mode.
constexpr bool	operator!= (const Key &a, const Key &b) noexcept
	Negation of operator==.

Detailed Description

A tonic and a diatonic mode, with the key signature they imply.

The key is modelled separately from its scale (SPEC-KEY-2): Signature() follows from the tonic's position on the circle of fifths and the mode, and a tonic whose signature would exceed seven sharps or flats (G# major) produces the invalid key. Spell() writes any pitch class in the key's context: diatonic pitch classes use the key's own letters; a chromatic one alters a diatonic note by a semitone, preferring the spelling with fewer accidentals and, on a tie, a raised note in sharp keys and a lowered note in flat keys (SPEC-KEY-3).

---

The documentation for this class was generated from the following file:

• src/MCC/Key/Key.h