Key signature

The key signature indicates the tonality in which a piece is played. It is denoted by a set of alterations (flats or sharps) at the start of the staff. The key signature may be altered:

\key pitch mode

Here, mode should be \major or \minor to get a key signature of pitch-major or pitch-minor, respectively. You may also use the standard mode names, also called church modes: \ionian, \dorian, \phrygian, \lydian, \mixolydian, \aeolian, and \locrian.

\relative {
  \key g \major
  fis''1
  f
  fis
}

Additional modes can be defined, by listing the alterations for each scale step when the mode starts on C.

freygish = #`((0 . ,NATURAL) (1 . ,FLAT) (2 . ,NATURAL)
    (3 . ,NATURAL) (4 . ,NATURAL) (5 . ,FLAT) (6 . ,FLAT))

\relative {
  \key c \freygish c'4 des e f
  \bar "||" \key d \freygish d es fis g
}

Accidentals in the key signature may be printed in octaves other than their traditional positions, or in multiple octaves, by using the flat-positions and sharp-positions properties of KeySignature. Entries in these properties specify the range of staff positions where accidentals will be printed. If a single position is specified in an entry, the accidentals are placed within the octave ending at that staff position.

\override Staff.KeySignature.flat-positions = #'((-5 . 5))
\override Staff.KeyCancellation.flat-positions = #'((-5 . 5))
\clef bass \key es \major es g bes d'
\clef treble \bar "||" \key es \major es' g' bes' d''

\override Staff.KeySignature.sharp-positions = #'(2)
\bar "||" \key b \major b' fis' b'2

Selected Snippets

Preventing natural signs from being printed when the key signature changes

When the key signature changes, natural signs are automatically printed to cancel any accidentals from previous key signatures. This may be prevented by setting to f the printKeyCancellation property in the Staff context.

\relative c' {
  \key d \major
  a4 b cis d
  \key g \minor
  a4 bes c d
  \set Staff.printKeyCancellation = ##f
  \key d \major
  a4 b cis d
  \key g \minor
  a4 bes c d
}

Non-traditional key signatures

The commonly used \key command sets the keyAlterations property, in the Staff context.

To create non-standard key signatures, set this property directly. The format of this command is a list:

\set Staff.keyAlterations =
  #`(((octave . step) . alter) ((octave . step) . alter) ...)

where, for each element in the list, octave specifies the octave (0 being the octave from middle C to the B above), step specifies the note within the octave (0 means C and 6 means B), and alter is ,SHARP ,FLAT ,DOUBLE-SHARP etc.

Alternatively, using the more concise format for each item in the list (step . alter) specifies the same alteration holds in all octaves.

For microtonal scales where a “sharp” is not 100 cents, alter refers to the alteration as a proportion of a 200-cent whole tone.

\include "arabic.ly"
\relative do' {
  \set Staff.keyAlterations = #`((0 . ,SEMI-FLAT)
                                 (1 . ,SEMI-FLAT)
                                 (2 . ,FLAT)
                                 (5 . ,FLAT)
                                 (6 . ,SEMI-FLAT))
%\set Staff.extraNatural = ##f
  re reb \dwn reb resd
  dod dob dosd \dwn dob |
  dobsb dodsd do do |
}

See also

Music Glossary: church mode, scordatura.

Learning Manual: Pitches and key signatures.

Snippets: Pitches.

Internals Reference: KeyChangeEvent, Key_engraver, Key_performer, KeyCancellation, KeySignature, key-signature-interface.