### 1.2.6 Special rhythmic concerns

#### Grace notes

Grace notes are ornaments that are written out. Grace notes are printed in a smaller font and take up no logical time in a measure.

c4 \grace c16 c4
\grace { c16[ d16] } c2


Lilypond also supports two special types of grace notes, the acciaccatura–an unmeasured grace note indicated by a slurred small note with a slashed stem–and the appoggiatura, which takes a fixed fraction of the main note and appears in small print without a slash.

\grace c8 b4
\acciaccatura d8 c4
\appoggiatura e8 d4
\acciaccatura { g16[ f] } e4


The placement of grace notes is synchronized between different staves. In the following example, there are two sixteenth grace notes for every eighth grace note

<< \new Staff { e2 \grace { c16[ d e f] } e2 }
\new Staff { c2 \grace { g8[ b] } c2 } >>


If you want to end a note with a grace, use the \afterGrace command. It takes two arguments: the main note, and the grace notes following the main note.

c1 \afterGrace d1 { c16[ d] } c1


This will put the grace notes after a space lasting 3/4 of the length of the main note. The default fraction 3/4 can be changed by setting afterGraceFraction. The following example shows the results from setting the space at the default, at 15/16, and finally at 1/2 of the main note.

<<
\new Staff {
c1 \afterGrace d1 { c16[ d] } c1
}
\new Staff {
#(define afterGraceFraction (cons 15 16))
c1 \afterGrace d1 { c16[ d] } c1
}
\new Staff {
#(define afterGraceFraction (cons 1 2))
c1 \afterGrace d1 { c16[ d] } c1
}
>>


The space between the main note and the grace note may also be specified using spacers. The following example places the grace note after a space lasting 7/8 of the main note.

\new Voice {
<< { d1^\trill_( }
{ s2 s4. \grace { c16[ d] } } >>
c1)
}


A \grace music expression will introduce special typesetting settings, for example, to produce smaller type, and set directions. Hence, when introducing layout tweaks to override the special settings, they should be placed inside the grace expression. The overrides should also be reverted inside the grace expression. Here, the grace note’s default stem direction is overriden and then reverted.

\new Voice {
\acciaccatura {
\stemDown
f16->
\stemNeutral
}
g4 e c2
}


#### Selected Snippets

The slash through the stem found in acciaccaturas can be applied in other situations:

\relative c'' {
\override Stem #'stroke-style = #"grace"
c8( d2) e8( f4)
}


The layout of grace expressions can be changed throughout the music using the function add-grace-property. The following example undefines the Stem direction for this grace, so that stems do not always point up.

\relative c'' {
\new Staff {
#(remove-grace-property 'Voice 'Stem 'direction)
\new Voice {
\acciaccatura { f16 } g4
\grace { d16[ e] } f4
\appoggiatura { a,32[ b c d] } e2
}
}
}


Another option is to change the variables startGraceMusic, stopGraceMusic, startAcciaccaturaMusic, stopAcciaccaturaMusic, startAppoggiaturaMusic, stopAppoggiaturaMusic. The default values of these can be seen in the file ly/grace-init.ly. By redefining them other effects may be obtained.

Grace notes may be forced to align with regular notes in other staves:

\relative c'' {
<<
\override Score.SpacingSpanner #'strict-grace-spacing = ##t
\new Staff {
c4
\afterGrace c4 { c16[ c8 c16] }
c4 r
}
\new Staff {
c16 c c c c c c c c4 r
}
>>
}


Music Glossary: grace notes, acciaccatura, appoggiatura.

Installed Files: ‘ly/grace-init.ly’.

Snippets: Rhythms.

Internals Reference: GraceMusic.

#### Known issues and warnings

A multi-note beamed acciaccatura is printed without a slash, and looks exactly the same as a multi-note beamed appoggiatura.

Grace note synchronization can also lead to surprises. Staff notation, such as key signatures, bar lines, etc., are also synchronized. Take care when you mix staves with grace notes and staves without, for example,

<< \new Staff { e4 \bar "|:" \grace c16 d2. }
\new Staff { c4 \bar "|:" d2. } >>


This can be remedied by inserting grace skips of the corresponding durations in the other staves. For the above example

<< \new Staff { e4 \bar "|:" \grace c16 d2. }
\new Staff { c4 \bar "|:" \grace s16 d2. } >>


Grace sections should only be used within sequential music expressions. Nesting or juxtaposing grace sections is not supported, and might produce crashes or other errors.

In an orchestral context, cadenzas present a special problem: when constructing a score that includes a measured cadenza or other solo passage, all other instruments should skip just as many notes as the length of the cadenza, otherwise they will start too soon or too late.

One solution to this problem is to use the functions mmrest-of-length and skip-of-length. These Scheme functions take a defined piece of music as an argument and generate a multi-measure rest or \skip exactly as long as the piece.

MyCadenza = \relative c' {
c4 d8 e f g g4
f2 g4 g
}

\new GrandStaff <<
\new Staff {
}
\new Staff {
c'1
c'1
}
>>


Snippets: Rhythms.

Time is administered by the Timing_translator, which by default is to be found in the Score context. An alias, Timing, is added to the context in which the Timing_translator is placed.

The following properties of Timing are used to keep track of timing within the score.

currentBarNumber

The current measure number. For an example showing the use of this property see Bar numbers.

measureLength

The length of the measures in the current time signature. For a 4/4 time this is 1, and for 6/8 it is 3/4. Its value determines when bar lines are inserted and how automatic beams should be generated.

measurePosition

The point within the measure where we currently are. This quantity is reset by subtracting measureLength whenever measureLength is reached or exceeded. When that happens, currentBarNumber is incremented.

timing

If set to true, the above variables are updated for every time step. When set to false, the engraver stays in the current measure indefinitely.

Timing can be changed by setting any of these variables explicitly. In the next example, the default 4/4 time signature is printed, but measureLength is set to 5/4. At 4/8 through the third measure, the measurePosition is advanced by 1/8 to 5/8, shortening that bar by 1/8. The next bar line then falls at 9/8 rather than 5/4.

\set Score.measureLength = #(ly:make-moment 5 4)
c1 c4
c1 c4
c4 c4
\set Score.measurePosition = #(ly:make-moment 5 8)
b4 b4 b8
c4 c1


As the example illustrates, ly:make-moment n m constructs a duration of n/m of a whole note. For example, ly:make-moment 1 8 is an eighth note duration and ly:make-moment 7 16 is the duration of seven sixteenths notes.