Automatic accidentals

There are many different conventions on how to typeset accidentals. LilyPond provides a function to specify which accidental style to use. This function is called as follows:

\new Staff <<
  \accidentalStyle voice
  { … }
>>

The accidental style normally applies to the current Staff (with the exception of the styles choral, piano and piano-cautionary, which are explained below). Optionally, the function can take a second argument that determines in which scope the style should be changed. For example, to use the same style in all staves of the current StaffGroup, use:

\accidentalStyle StaffGroup.voice

The following accidental styles are supported. To demonstrate each style, we use the following example:

musicA = {
  <<
    \relative {
      cis''8 fis, bes4 <a cis>8 f bis4 |
      cis2. <c, g'>4 |
    }
    \\
    \relative {
      ais'2 cis, |
      fis8 b a4 cis2 |
    }
  >>
}

musicB = {
  \clef bass
  \new Voice {
    \voiceTwo \relative {
      <fis a cis>8[ <fis a cis>
      \change Staff = up
      cis' cis
      \change Staff = down
      <fis, a> <fis a>]
      \showStaffSwitch
      \change Staff = up
      dis'4 |
      \change Staff = down
      <fis, a cis>4 gis <f a d>2 |
    }
  }
}

\new PianoStaff {
  <<
    \new Staff = "up" {
      \accidentalStyle default
      \musicA
    }
    \new Staff = "down" {
      \accidentalStyle default
      \musicB
    }
  >>
}

Note that the last lines of this example can be replaced by the following, as long as the same accidental style should be used in both staves.

\new PianoStaff {
  <<
    \new Staff = "up" {
      %%% change the next line as desired:
      \accidentalStyle Score.default
      \musicA
    }
    \new Staff = "down" {
      \musicB
    }
  >>
}

default

This is the default typesetting behavior. It corresponds to eighteenth-century common practice: accidentals are remembered to the end of the measure in which they occur and only in their own octave. Thus, in the example below, no natural signs are printed before the b in the second measure or the last c:

voice

The normal behavior is to remember the accidentals at Staff-level. In this style, however, accidentals are typeset individually for each voice. Apart from that, the rule is similar to default.

As a result, accidentals from one voice do not get canceled in other voices, which is often an unwanted result: in the following example, it is hard to determine whether the second a should be played natural or sharp. The voice option should therefore be used only if the voices are to be read solely by individual musicians. If the staff is to be used by one musician (e.g., a conductor or in a piano score) then modern or modern-cautionary should be used instead.

modern

This rule corresponds to the common practice in the twentieth century. It omits some extra natural signs, which were traditionally prefixed to a sharp following a double sharp, or a flat following a double flat. The modern rule prints the same accidentals as default, with two additions that serve to avoid ambiguity: after temporary accidentals, cancellation marks are printed also in the following measure (for notes in the same octave) and, in the same measure, for notes in other octaves. Hence the naturals before the b and the c in the second measure of the upper staff:

modern-cautionary

This rule is similar to modern, but the ‘extra’ accidentals are printed as cautionary accidentals (with parentheses). They can also be printed at a different size by overriding AccidentalCautionary’s font-size property.

modern-voice

This rule is used for multi-voice accidentals to be read both by musicians playing one voice and musicians playing all voices. Accidentals are typeset for each voice, but they are canceled across voices in the same Staff. Hence, the a in the last measure is canceled because the previous cancellation was in a different voice, and the d in the lower staff is canceled because of the accidental in a different voice in the previous measure:

modern-voice-cautionary

This rule is the same as modern-voice, but with the extra accidentals (the ones not typeset by voice) typeset as cautionaries. Even though all accidentals typeset by default are typeset with this rule, some of them are typeset as cautionaries.

piano

This rule reflects twentieth-century practice for piano notation. Its behavior is very similar to modern style, but here accidentals also get canceled across the staves in the same GrandStaff or PianoStaff, hence all the cancellations of the final notes.

This accidental style applies to the current GrandStaff or PianoStaff unless qualified with a second argument.

piano-cautionary

This is the same as piano but with the extra accidentals typeset as cautionaries.

choral

This rule is a combination of the modern-voice and the piano style. It shows all accidentals required for singers that only follow their own voice, as well as additional accidentals for readers that follow all voices of an entire ChoirStaff simultaneously.

This accidental style applies to the current ChoirStaff unless qualified with a second argument.

choral-cautionary

This is the same as choral but with the extra accidentals typeset as cautionaries.

neo-modern

This rule reproduces a common practice in contemporary music: accidentals are printed like with modern, but they are printed again if the same note appears later in the same measure – except if the note is immediately repeated.

neo-modern-cautionary

This rule is similar to neo-modern, but the ‘extra’ accidentals are printed as cautionary accidentals (with parentheses). They can also be printed at a different size by overriding AccidentalCautionary’s font-size property.

neo-modern-voice

This rule is used for multi-voice accidentals to be read both by musicians playing one voice and musicians playing all voices. Accidentals are typeset for each voice as with neo-modern, but they are canceled across voices in the same Staff.

neo-modern-voice-cautionary

This rule is similar to neo-modern-voice, but the extra accidentals are printed as cautionary accidentals.

dodecaphonic

This rule reflects a practice introduced by composers at the beginning of the 20th century, in an attempt to abolish the hierarchy between natural and non-natural notes. With this style, every note gets an accidental sign, including natural signs.

dodecaphonic-no-repeat

Like with the dodecaphonic accidental style every note gets an accidental sign by default, but accidentals are suppressed for pitches immediately repeated within the same staff.

dodecaphonic-first

Similar to the dodecaphonic accidental style every pitch gets an accidental sign, but only the first time it is encountered in a measure. Accidentals are only remembered for the actual octave but throughout voices.

teaching

This rule is intended for students, and makes it easy to create scale sheets with automatically created cautionary accidentals. Accidentals are printed like with modern, but cautionary accidentals are added for all sharp or flat tones specified by the key signature, except if the note is immediately repeated.

no-reset

This is the same as default but with accidentals lasting ‘forever’ and not only within the same measure:

forget

This is the opposite of no-reset: Accidentals are not remembered at all – and hence all accidentals are typeset relative to the key signature, regardless of what came before in the music.

See also

Snippets: Pitches.

Internals Reference: Accidental, Accidental_engraver, GrandStaff, PianoStaff, Staff, AccidentalSuggestion, AccidentalPlacement, accidental-suggestion-interface.

Known issues and warnings

Simultaneous notes are not considered in the automatic determination of accidentals; only previous notes and the key signature are taken into account. Forcing accidentals with ‘!’ or ‘?’ may be required when the same note name occurs simultaneously with different alterations, as in <f! fis!>.

\relative c' <<
  { fis8 g } \\
  { f! f }
>>

A more sophisticated solution is given in LSR snippet 1172.

In alternative endings, cautionary cancellation should be based on the previous played measure, but it is based on the previous printed measure. In the following example, the natural c in the second alternative does not need a natural sign:

The following workaround can be used: define a function that locally changes the accidental style to forget:

forget = #(define-music-function (music) (ly:music?) #{
  \accidentalStyle forget
  #music
  \accidentalStyle modern
#})
{
  \accidentalStyle modern
  \time 2/4
  \repeat volta 2 {
    c'2
  }
  \alternative {
     \volta 1 { cis' }
     \volta 2 { \forget c' }
  }
}