Split Rhythms away from *notation.

[lilypond.git] / Documentation / user / rhythms.itely

@c -*- coding: utf-8; mode: texinfo; -*-

@node Rhythms
@section Rhythms

This section discusses rhythms, durations, and bars.

@menu
* Writing rhythms::             
* Writing rests::               
* Displaying rhythms::          
* Beams::                       
* Bars::                        
* Special rhythmic concerns::   
@end menu


@node Writing rhythms
@subsection Writing rhythms

@anchor{Durations}
@unnumberedsubsubsec Durations

@cindex duration
@funindex \longa
@funindex \breve
@funindex \maxima

In Note, Chord, and Lyrics mode, durations are designated by numbers and
dots: durations are entered as their reciprocal values.  For example, a
quarter note is entered using a @code{4} (since it is a 1/4 note), while
a half note is entered using a @code{2} (since it is a 1/2 note).  For
notes longer than a whole you must use the @code{\longa} and
@code{\breve} commands

@example
c'\breve
c'1 c'2 c'4 c'8 c'16 c'32 c'64 c'64
r\longa r\breve
r1 r2 r4 r8 r16 r32 r64 r64
@end example

@lilypond[quote]
\score {
\relative c'' {
    a\breve*1/2 \autoBeamOff
    a1 a2 a4 a8 a16 a32 a64 a64
   \bar "empty"
   \break
    r\longa*1/4 r\breve *1/2
    r1 r2 r4 r8 r16 r32 r64 r64
  }
  \layout {
    ragged-right = ##t
    indent=0\mm
    \context {
      \Score
        \remove "Bar_number_engraver"
    }
    \context {
      \Staff
        \remove "Clef_engraver"
        \override StaffSymbol #'transparent = ##t
        \override TimeSignature #'transparent = ##t
        \override BarLine #'transparent = ##t
        \consists "Pitch_squash_engraver"
    }
  }
}
@end lilypond

If the duration is omitted then it is set to the previously entered
duration.  The default for the first note is a quarter note.

@lilypond[quote,ragged-right,verbatim,fragment]
{ a a a2 a a4 a a1 a }
@end lilypond


@anchor{Augmentation dots}
@unnumberedsubsubsec Augmentation dots

@funindex .

To obtain dotted note lengths, simply add a dot (@samp{.}) to
the number.  Double-dotted notes are produced in a similar way.

@lilypond[quote,ragged-right,fragment,verbatim]
a'4 b' c''4. b'8 a'4. b'4.. c''8.
@end lilypond

@refcommands

Dots are normally moved up to avoid staff lines, except in polyphonic
situations.  The following commands may be used to force a particular
direction manually

@funindex \dotsUp
@code{\dotsUp},
@funindex \dotsDown
@code{\dotsDown},
@funindex \dotsNeutral
@code{\dotsNeutral}.

@seealso

Program reference: @internalsref{Dots}, and @internalsref{DotColumn}.


@anchor{Tuplets}
@unnumberedsubsubsec Tuplets

@cindex tuplets
@cindex triplets
@funindex \times

Tuplets are made out of a music expression by multiplying all durations
with a fraction

@example
\times @var{fraction} @var{musicexpr}
@end example

@noindent
The duration of @var{musicexpr} will be multiplied by the fraction.
The fraction's denominator will be printed over the notes, optionally
with a bracket.  The most common tuplet is the triplet in which 3
notes have the length of 2, so the notes are 2/3 of their written
length

@lilypond[quote,ragged-right,fragment,verbatim]
g'4 \times 2/3 {c'4 c' c'} d'4 d'4
@end lilypond

Tuplets may be nested, for example,

@lilypond[fragment,ragged-right,verbatim,relative=2]
\override TupletNumber #'text = #tuplet-number::calc-fraction-text
\times 4/6 {
  a4 a
  \times 3/5 { a a a a a }
}
@end lilypond

@refcommands

@funindex \tupletUp
@code{\tupletUp},
@funindex \tupletDown
@code{\tupletDown},
@funindex \tupletNeutral
@code{\tupletNeutral}.


@commonprop

@funindex tupletNumberFormatFunction
@cindex tuplet formatting

The property @code{tupletSpannerDuration} specifies how long each
bracket should last.  With this, you can make lots of tuplets while
typing @code{\times} only once, thus saving lots of typing.  In the next
example, there are two triplets shown, while @code{\times} was only
used once

@lilypond[quote,fragment,relative=2,ragged-right,verbatim]
\set tupletSpannerDuration = #(ly:make-moment 1 4)
\times 2/3 { c8 c c c c c }
@end lilypond

@noindent
For more information about @code{make-moment}, see
@ref{Time administration}.

The format of the number is determined by the property @code{text} in
@code{TupletNumber}.  The default prints only the denominator, but if
it is set to the function @code{tuplet-number::calc-fraction-text},
@var{num}:@var{den} will be printed instead.

To avoid printing tuplet numbers, use

@lilypond[quote,fragment,relative=2,ragged-right,verbatim]
\times 2/3 { c8 c c } \times 2/3 { c8 c c }
\override TupletNumber #'transparent = ##t
\times 2/3 { c8 c c } \times 2/3 { c8 c c }
@end lilypond

Use the @code{\tweak} function to override nested tuplets beginning at the
same music moment.  In this example, @code{\tweak} specifies fraction
text for the
outer @code{TupletNumber} and denominator text for the @code{TupletNumber}
of the first of the three inner tuplets.

@lilypond[quote,ragged-right,verbatim]
\new Staff {
  \tweak #'text #tuplet-number::calc-fraction-text
  \times 4/3 {
     \tweak #'text #tuplet-number::calc-denominator-text
     \times 2/3 { c'8[ c'8 c'8] }
     \times 2/3 { c'8[ c'8 c'8] }
     \times 2/3 { c'8[ c'8 c'8] }
  }
}
@end lilypond

Here @code{\tweak} and @code{\override} work together to specify
@code{TupletBracket} direction.  The first @code{\tweak} positions
the @code{TupletBracket} of the outer
tuplet above the staff.  The second @code{\tweak} positions the
@code{TupletBracket} of the first of the three inner tuplets below the
staff.  Note that this pair of @code{\tweak} functions affects only
the outer tuplet and the first of the three inner tuplets because only
those two tuplets begin at the same music moment.  We use @code{\override}
in the usual way to position the @code{TupletBrackets} of
the second and third of the inner tuplets below the staff.

@lilypond[quote,ragged-right,verbatim]
\new Staff {
  \tweak #'text #tuplet-number::calc-fraction-text
  \tweak #'direction #up
  \times 4/3 {
     \tweak #'direction #down
     \times 2/3 { c'8[ c'8 c'8] }
     \override TupletBracket #'direction = #down
     \times 2/3 { c'8[ c'8 c'8] }
     \times 2/3 { c'8[ c'8 c'8] }
  }
}
@end lilypond

Tuplet brackets can be made to run to prefatory matter or
the next note

@lilypond[ragged-right]
\new RhythmicStaff {
  \set tupletFullLength = ##t
  \time 4/4
  \times 4/5 {
    c4 c1
  }
  \set tupletFullLengthNote = ##t
  \time 2/4
  \times 2/3 {
    c4 c c 
  }
  \time 3/4
  c4 
}
@end lilypond


@seealso

Program reference: @internalsref{TupletBracket},
@internalsref{TupletNumber}, and @internalsref{TimeScaledMusic}.



@anchor{Scaling durations}
@unnumberedsubsubsec Scaling durations

You can alter the length of duration by a fraction @var{N/M}
appending @samp{*@var{N/M}} (or @samp{*@var{N}} if @var{M=1}).  This
will not affect the appearance of the notes or rests produced.  These
may be combined such as @samp{*M*N}.

In the following example, the first three notes take up exactly two
beats, but no triplet bracket is printed.

@lilypond[quote,ragged-right,fragment,relative=2,verbatim]
\time 2/4
a4*2/3 gis4*2/3 a4*2/3
a4 a4 a4*2
b16*4 c4
@end lilypond


@seealso

This manual: @ref{Tuplets}.


@node Writing rests
@subsection Writing rests

@anchor{Rests}
@unnumberedsubsubsec Rests
@cindex Rests

@funindex \rest
@funindex r

Rests are entered like notes with the note name @code{r}

@lilypond[fragment,quote,ragged-right,verbatim]
r1 r2 r4 r8
@end lilypond

Whole bar rests, centered in middle of the bar,
must be done with multi-measure rests.  They can be used for a
single bar as well as many bars, and are discussed in
@ref{Multi measure rests}.

To explicitly specify a rest's vertical position, write a note
followed by @code{\rest}.  A rest will be placed in the position
where the note would appear,

@lilypond[fragment,quote,ragged-right,verbatim]
a'4\rest d'4\rest
@end lilypond

@noindent
This makes manual formatting of
polyphonic music much easier, since the automatic rest collision
formatter will leave these rests alone.

@seealso

Program reference: @internalsref{Rest}.


@anchor{Skips}
@unnumberedsubsubsec Skips

@cindex Skip
@cindex Invisible rest
@cindex Space note
@funindex \skip
@funindex s

An invisible rest (also called a @q{skip}) can be entered like a note
with note name @samp{s} or with @code{\skip @var{duration}}

@lilypond[fragment,quote,ragged-right,verbatim,relative=2]
a4 a4 s4 a4 \skip 1 a4
@end lilypond

The @code{s} syntax is only available in note mode and chord mode.  In
other situations, for example, when entering lyrics, you should use
the @code{\skip} command

@lilypond[quote,ragged-right,verbatim]
<<
  \relative { a'2 a2 }
  \new Lyrics \lyricmode { \skip 2 bla2 }
>>
@end lilypond

The skip command is merely an empty musical placeholder.  It does not
produce any output, not even transparent output.

The @code{s} skip command does create @internalsref{Staff} and
@internalsref{Voice} when necessary, similar to note and rest
commands.  For example, the following results in an empty staff.

@lilypond[quote,ragged-right,verbatim]
{ s4 }
@end lilypond

The fragment @code{@{ \skip 4 @} } would produce an empty page.

@seealso

Program reference: @internalsref{SkipMusic}.


@anchor{Multi measure rests}
@unnumberedsubsubsec Multi measure rests

@cindex multi measure rests
@cindex full measure rests
@cindex Rests, multi measure
@cindex Rests, full measure
@cindex whole rests for a full measure
@funindex R

Rests for one full measure (or many bars) are entered using @samp{R}.  It
is specifically meant for full bar rests and for entering parts: the rest
can expand to fill a score with rests, or it can be printed as a single
multi-measure rest.  This expansion is controlled by the property
@code{Score.skipBars}.  If this is set to true, empty measures will not
be expanded, and the appropriate number is added automatically

@lilypond[quote,ragged-right,fragment,verbatim]
\time 4/4 r1 | R1 | R1*2 \time 3/4 R2. \time 2/4 R2 \time 4/4
\set Score.skipBars = ##t R1*17 R1*4
@end lilypond

The @code{1} in @code{R1} is similar to the duration notation used for
notes.  Hence, for time signatures other than 4/4, you must enter other
durations.  This can be done with augmentation dots or fractions

@lilypond[quote,ragged-right,fragment,verbatim]
\set Score.skipBars = ##t
\time 3/4
R2. | R2.*2
\time 13/8
R1*13/8
R1*13/8*12 |
\time 10/8 R4*5*4 |
@end lilypond

An @code{R} spanning a single measure is printed as either a whole rest
or a breve, centered in the measure regardless of the time signature.

If there are only a few measures of rest, LilyPond prints @q{church rests}
(a series of rectangles) in the staff.  To replace that with a simple
rest, use @code{MultiMeasureRest.expand-limit}.

@lilypond[quote,ragged-right,fragment,verbatim]
\set Score.skipBars = ##t
R1*2 | R1*5 | R1*9
\override MultiMeasureRest #'expand-limit = 1
R1*2 | R1*5 | R1*9
@end lilypond

@cindex text on multi-measure rest
@cindex script on multi-measure rest
@cindex fermata on multi-measure rest

Texts can be added to multi-measure rests by using the
@var{note}-@code{markup} syntax @ref{Text markup}.
A variable (@code{\fermataMarkup}) is provided for
adding fermatas

@lilypond[quote,ragged-right,verbatim,fragment]
\set Score.skipBars = ##t
\time 3/4
R2.*10^\markup { \italic "ad lib." }
R2.^\fermataMarkup
@end lilypond

Warning!  This text is created by @code{MultiMeasureRestText}, not
@code{TextScript}.

@lilypond[quote,ragged-right,verbatim,fragment]
\override TextScript #'padding = #5
R1^"low"
\override MultiMeasureRestText #'padding = #5
R1^"high"
@end lilypond

If you want to have text on the left end of a multi-measure rest,
attach the text to a zero-length skip note, i.e.,

@example
s1*0^"Allegro"
R1*4
@end example


@seealso

Program reference: @internalsref{MultiMeasureRestMusicGroup},
@internalsref{MultiMeasureRest}.

The layout object @internalsref{MultiMeasureRestNumber} is for the
default number, and @internalsref{MultiMeasureRestText} for user
specified texts.


@refbugs

It is not possible to use fingerings (e.g., @code{R1-4}) to put numbers
over multi-measure rests.  And the pitch of multi-measure rests (or
staff-centered rests) can not be influenced.

@cindex condensing rests

There is no way to automatically condense multiple rests into a single
multi-measure rest.  Multi-measure rests do not take part in rest
collisions.

Be careful when entering multi-measure rests followed by whole
notes.  The following will enter two notes lasting four measures each
@example
R1*4 cis cis
@end example
When @code{skipBars} is set, the result will look OK, but the bar
numbering will be off.



@node Displaying rhythms
@subsection Displaying rhythms

@anchor{Time signature}
@unnumberedsubsubsec Time signature

@cindex Time signature
@cindex meter
@funindex \time

Time signature indicates the metrum of a piece: a regular pattern of
strong and weak beats.  It is denoted by a fraction at the start of the
staff.

The time signature is set with the @code{\time} command

@lilypond[quote,ragged-right,fragment,verbatim]
\time 2/4 c'2 \time 3/4 c'2.
@end lilypond

@commonprop

The symbol that is printed can be customized with the @code{style}
property.  Setting it to @code{#'()} uses fraction style for 4/4 and
2/2 time,

@lilypond[fragment,quote,ragged-right,verbatim]
\time 4/4 c'1
\time 2/2 c'1
\override Staff.TimeSignature #'style = #'()
\time 4/4 c'1
\time 2/2 c'1
@end lilypond

There are many more options for its layout.  See @ref{Ancient time
signatures}, for more examples.

@code{\time} sets the property @code{timeSignatureFraction},
@code{beatLength} and @code{measureLength} in the @code{Timing}
context, which is normally aliased to @internalsref{Score}.  The
property @code{measureLength} determines where bar lines should be
inserted, and how automatic beams should be generated.  Changing the
value of @code{timeSignatureFraction} also causes the symbol to be
printed.

More options are available through the Scheme function
@code{set-time-signature}.  In combination with the
@internalsref{Measure_grouping_engraver}, it will create
@internalsref{MeasureGrouping} signs.  Such signs ease reading
rhythmically complex modern music.  In the following example, the 9/8
measure is subdivided in 2, 2, 2 and 3.  This is passed to
@code{set-time-signature} as the third argument @code{(2 2 2 3)}

@lilypond[quote,ragged-right,verbatim]
\score {
  \relative c'' {
    #(set-time-signature 9 8 '(2 2 2 3))
    g8[ g] d[ d] g[ g] a8[( bes g]) |
    #(set-time-signature 5 8 '(3 2))
    a4. g4
  }
  \layout {
    \context {
      \Staff
      \consists "Measure_grouping_engraver"
    }
  }
}
@end lilypond


@seealso

Program reference: @internalsref{TimeSignature}, and
@internalsref{Timing_translator}.

Examples: @lsr{contemporary,compound-time-signature.ly}.


@refbugs

Automatic beaming does not use the measure grouping specified with
@code{set-time-signature}.


@anchor{Upbeats}
@unnumberedsubsubsec Upbeats

@cindex anacrusis
@cindex upbeat
@cindex partial measure
@cindex measure, partial
@cindex shorten measures
@funindex \partial

Partial measures, such as an anacrusis or upbeat, are entered using the

@lilypond[quote,ragged-right,fragment,verbatim,relative=2]
\partial 16*5 c16 cis d dis e | a2. c,4 | b2
@end lilypond

The syntax for this command is

@example
\partial @var{duration}
@end example

where @code{duration} is the rhythmic length to be added before
the next bar.

This is internally translated into

@example
\set Timing.measurePosition = -@var{length of duration}
@end example

The property @code{measurePosition} contains a rational number
indicating how much of the measure has passed at this point.  Note
that this is a negative number; @code{\partial 4} is internally
translated to mean @qq{there is a quarter note left in the bar.}


@refbugs

This command does not take into account grace notes at the start of
the music.  When a piece starts with graces notes in the pickup, then
the @code{\partial} should follow the grace notes

@lilypond[verbatim,quote,ragged-right,relative,fragment]
\grace f16
\partial 4
g4
a2 g2
@end lilypond

@code{\partial} is only intended to be used at the beginning of a
piece.  If you use it after the beginning, some odd warnings may
occur.


@anchor{Unmetered music}
@unnumberedsubsubsec Unmetered music

@cindex cadenza
@funindex \cadenzaOn
@funindex \cadenzaOff

Bar lines and bar numbers are calculated automatically.  For unmetered
music (cadenzas, for example), this is not desirable.  To turn off
automatic bar lines and bar numbers, use the commands @code{\cadenzaOn}
and @code{\cadenzaOff}.

@lilypond[verbatim,quote,ragged-right,relative=2,fragment]
c4 d e d
\cadenzaOn
c4 c d8 d d f4 g4.
\cadenzaOff
\bar "|"
d4 e d c
@end lilypond


@refbugs

LilyPond will only insert line breaks and page breaks at a
barline.  Unless the unmetered music ends before the end of
the staff line, you will need to insert
invisible bar lines

@example
\bar ""
@end example

@noindent
to indicate where breaks can occur.


@anchor{Polymetric notation}
@unnumberedsubsubsec Polymetric notation

@cindex double time signatures
@cindex signatures, polymetric
@cindex polymetric signatures
@cindex meter, polymetric

Double time signatures are not supported explicitly, but they can be
faked.  In the next example, the markup for the time signature is
created with a markup text.  This markup text is inserted in the
@internalsref{TimeSignature} grob. See also
@lsr{contemporary,compound-time-signature}.

@lilypond[verbatim,ragged-right]
% create 2/4 + 5/8
tsMarkup =\markup {
  \override #'(baseline-skip . 2) \number {
    \column { "2" "4" }
    \vcenter "+"
    \bracket \column { "5" "8" }
  }
}

{
  \override Staff.TimeSignature #'stencil = #ly:text-interface::print
  \override Staff.TimeSignature #'text = #tsMarkup
  \time 3/2
  c'2 \bar ":" c'4 c'4.
}
@end lilypond

Each staff can also have its own time signature.  This is done by
moving the @internalsref{Timing_translator} to the @internalsref{Staff}
context.

@example
\layout @{
  \context @{ \Score
     \remove "Timing_translator"
     \remove "Default_bar_line_engraver"
  @}
  \context @{
    \Staff
    \consists "Timing_translator"
    \consists "Default_bar_line_engraver"
  @}

@}
@end example


Now, each staff has its own time signature.
@example
<<
  \new Staff @{
    \time 3/4
    c4 c c | c c c |
  @}
  \new Staff @{
    \time 2/4
    c4 c | c c | c c
  @}
  \new Staff @{
    \time 3/8
    c4. c8 c c c4. c8 c c
  @}
>>
@end example

@lilypond[quote,ragged-right]
\layout{
  \context{
     \Score
     \remove "Timing_translator"
     \remove "Default_bar_line_engraver"
    }
  \context{ \Staff
    \consists "Timing_translator"
    \consists "Default_bar_line_engraver"
  }
}

\relative c' <<
  \new Staff {
    \time 3/4
    c4 c c | c c c |
  }
  \new Staff {
    \time 2/4
    c4 c | c c | c c
  }
  \new Staff {
    \time 3/8
    c4. c8 c c c4. c8 c c
  }
>>
@end lilypond


A different form of polymetric notation is where note lengths have
different values across staves.

This notation can be created by setting a common time signature for
each staff but replacing it manually using
@code{timeSignatureFraction} to the desired fraction.  Then the printed
durations in each staff are scaled to the common time signature.
The latter is done with @code{\compressMusic}, which is used similar
to @code{\times}, but does not create a tuplet bracket. The syntax is
@example
\compressMusic #'(@var{numerator} . @var{denominator}) @var{musicexpr}
@end example



In this example, music with the time signatures of 3/4, 9/8, and 10/8 are
used in parallel.  In the second staff, shown durations are multiplied by
2/3, so that 2/3 * 9/8 = 3/4, and in the third staff, shown durations are
multiplied by 3/5, so that 3/5 * 10/8 = 3/4.

@lilypond[quote,ragged-right,verbatim,fragment]
\relative c' { <<
  \new Staff {
    \time 3/4
    c4 c c | c c c |
  }
  \new Staff {
    \time 3/4
    \set Staff.timeSignatureFraction = #'(9 . 8)
    \compressMusic #'(2 . 3)
      \repeat unfold 6 { c8[ c c] }
  }
  \new Staff {
    \time 3/4
    \set Staff.timeSignatureFraction = #'(10 . 8)
    \compressMusic #'(3 . 5) {
      \repeat unfold 2 { c8[ c c] }
      \repeat unfold 2 { c8[ c] }
      | c4. c4. \times 2/3 { c8 c c } c4
    }
  }
>> }
@end lilypond


@refbugs

When using different time signatures in parallel, the spacing is
aligned vertically, but bar lines distort the regular spacing.


@anchor{Automatic note splitting}
@unnumberedsubsubsec Automatic note splitting

Long notes can be converted automatically to tied notes.  This is done
by replacing the @internalsref{Note_heads_engraver} by the
@internalsref{Completion_heads_engraver}.
In the following examples, notes crossing the bar line are split and tied.

@lilypond[quote,fragment,verbatim,relative=1,line-width=12\cm]
\new Voice \with {
  \remove "Note_heads_engraver"
  \consists "Completion_heads_engraver"
} {
  c2. c8 d4 e f g a b c8 c2 b4 a g16 f4 e d c8. c2
}
@end lilypond

This engraver splits all running notes at the bar line, and inserts
ties.  One of its uses is to debug complex scores: if the measures are
not entirely filled, then the ties exactly show how much each measure
is off.

If you want to allow line breaking on the bar lines where
@internalsref{Completion_heads_engraver} splits notes, you must
also remove @internalsref{Forbid_line_break_engraver}.


@refbugs

Not all durations (especially those containing tuplets) can be
represented exactly with normal notes and dots, but the engraver will
not insert tuplets.

@code{Completion_heads_engraver} only affects notes; it does not split
rests.


@seealso

Program reference: @internalsref{Completion_heads_engraver}.




@node Beams
@subsection Beams

@anchor{Automatic beams}
@unnumberedsubsubsec Automatic beams

LilyPond inserts beams automatically

@lilypond[quote,ragged-right,fragment,verbatim,relative=2]
\time 2/4 c8 c c c \time 6/8 c c c c8. c16 c8
@end lilypond

When these automatic decisions are not good enough, beaming can be
entered explicitly.  It is also possible to define beaming patterns
that differ from the defaults.  See @ref{Setting automatic beam behavior},
for details.

Individual notes may be marked with @code{\noBeam} to prevent them
from being beamed

@lilypond[quote,ragged-right,fragment,verbatim,relative=2]
\time 2/4 c8 c\noBeam c c
@end lilypond


@seealso

Program reference: @internalsref{Beam}.


@anchor{Manual beams}
@unnumberedsubsubsec Manual beams

@cindex beams, manual
@funindex ]
@funindex [

In some cases it may be necessary to override the automatic beaming
algorithm.  For example, the autobeamer will not put beams over rests
or bar lines.  Such beams are specified manually by marking the begin
and end point with @code{[} and @code{]}

@lilypond[quote,ragged-right,fragment,relative=1,verbatim]
{
  r4 r8[ g' a r8] r8 g[ | a] r8
}
@end lilypond


@commonprop

@funindex stemLeftBeamCount
@funindex stemRightBeamCount


LilyPond can automatically determine beaming patterns within a beam,
but this automatic behavior can sometimes produce odd results;
therefore the @code{stemLeftBeamCount} and @code{stemRightBeamCount} properties can
be used to override the defaults.  If
either property is set, its value will be used only once, and then it
is erased.

@lilypond[quote,ragged-right,fragment,relative=1,verbatim]
{
   f8[ r16
      f g a]
   f8[ r16
   \set stemLeftBeamCount = #1
      f g a]
}
@end lilypond

The property @code{subdivideBeams} can be set in order to subdivide
all 16th or shorter beams at beat positions, as defined by the
@code{beatLength} property.

@lilypond[fragment,quote,relative=2,verbatim]
c16[ c c c c c c c]
\set subdivideBeams = ##t
c16[ c c c c c c c]
\set Score.beatLength = #(ly:make-moment 1 8)
c16[ c c c c c c c]
@end lilypond
@funindex subdivideBeams

@noindent
For more information about @code{make-moment}, see
@ref{Time administration}.

Line breaks are normally forbidden when beams cross bar lines.  This
behavior can be changed by setting @code{breakable}.

@funindex breakable

@cindex beams and line breaks
@cindex beams, kneed
@cindex kneed beams
@cindex auto-knee-gap

Kneed beams are inserted automatically when a large gap is detected
between the note heads.  This behavior can be tuned through the
@code{auto-knee-gap} object.


@refbugs

Automatically kneed cross-staff beams cannot be used together with
hidden staves.  See @ref{Hiding staves}.

@c Is this still true with skyline spacing stuff? -J.Mandereau
Beams do not avoid collisions with symbols around the notes, such as
texts and accidentals.


@anchor{Feathered beams}
@unnumberedsubsubsec Feathered beams

Feathered beams are printed by setting the @code{grow-direction}
property of a @code{Beam}.  The @code{\featherDurations} function
can be used to adjust note durations.

@lilypond[ragged-right,relative=1,fragment,verbatim,quote]
\override Beam #'grow-direction = #LEFT
\featherDurations #(ly:make-moment 5 4) 
{
  c16[ c c c c c c]
}
@end lilypond

@refbugs

The @code{\featherDurations} command only works with very short
music snippets.


@node Bars
@subsection Bars


@anchor{Bar check}
@unnumberedsubsubsec Bar check

@cindex Bar check
@funindex barCheckSynchronize
@funindex |

Bar checks help detect errors in the durations.  A bar check is
entered using the bar symbol, @samp{|}.  Whenever it is encountered
during interpretation, it should fall on a measure boundary.  If it
does not, a warning is printed.  In the next example, the second bar
check will signal an error
@example
\time 3/4 c2 e4 | g2 |
@end example

Bar checks can also be used in lyrics, for example

@example
\lyricmode @{
  \time 2/4
  Twin -- kle | Twin -- kle
@}
@end example

Failed bar checks are caused by entering incorrect
durations.  Incorrect durations often completely garble up the score,
especially if the score is polyphonic, so a good place to start correcting
input is by scanning for failed bar checks and incorrect durations.

@funindex |
@funindex pipeSymbol

It is also possible to redefine the meaning of @code{|}.  This is done
by assigning a music expression to @code{pipeSymbol},

@lilypond[quote,ragged-right,verbatim]
pipeSymbol = \bar "||"

{ c'2 c' | c'2 c' }
@end lilypond


@anchor{Bar lines}
@unnumberedsubsubsec Bar lines

@cindex Bar lines
@funindex \bar
@cindex measure lines
@cindex repeat bars

Bar lines delimit measures, but are also used to indicate
repeats.  Normally they are inserted automatically.  Line
breaks may only happen on bar lines.

Special types of bar lines can be forced with the @code{\bar} command

@lilypond[quote,ragged-right,relative=2,fragment,verbatim]
c4 \bar "|:" c4
@end lilypond

The following bar types are available

@lilypondfile[ragged-right,quote]{bar-lines.ly}

In addition, you can specify @code{"||:"}, which is equivalent to 
@code{"|:"} except at line breaks, where it gives a double bar line at
the end of the line and a start repeat at the beginning of the next
line. 

To allow a line break where there is no visible bar line, use

@example
\bar ""
@end example

@noindent
This will insert an invisible bar line and allow line breaks at this
point (without increasing the bar number counter).

In scores with many staves, a @code{\bar} command in one staff is
automatically applied to all staves.  The resulting bar lines are
connected between different staves of a @code{StaffGroup},
@code{PianoStaff}, or @code{GrandStaff}.

@lilypond[quote,ragged-right,fragment,verbatim]
<<
  \new StaffGroup <<
    \new Staff {
      e'4 d'
      \bar "||"
      f' e'
    }
    \new Staff { \clef bass c4 g e g }
  >>
  \new Staff { \clef bass c2 c2 }
>>
@end lilypond


@commonprop

@funindex whichBar
@funindex repeatCommands
@funindex defaultBarType

The command @code{\bar }@var{bartype} is a short cut for doing
@code{\set Timing.whichBar = }@var{bartype}.  Whenever @code{whichBar}
is set to a string, a bar line of that type is created.

A bar line is created whenever the @code{whichBar} property is set.
At the start of a measure it is set to the contents of
@code{Timing.defaultBarType}.  The contents of @code{repeatCommands} are
used
to override default measure bars.

You are encouraged to use @code{\repeat} for repetitions.  See
@ref{Repeats}.


@seealso

In this manual: @ref{Repeats}, @ref{System start delimiters}.

Program reference: @internalsref{BarLine} (created at
@internalsref{Staff} level), @internalsref{SpanBar} (across staves).


@anchor{Bar numbers}
@unnumberedsubsubsec Bar numbers

@cindex Bar numbers
@cindex measure numbers
@funindex currentBarNumber

Bar numbers are printed by default at the start of the line.  The
number itself is stored in the @code{currentBarNumber} property, which
is normally updated automatically for every measure.

@lilypond[verbatim,ragged-right,quote,fragment,relative]
\repeat unfold 4 {c4 c c c} \break
\set Score.currentBarNumber = #50
\repeat unfold 4 {c4 c c c}
@end lilypond

Bar numbers may only be printed at bar lines; to print a bar
number at the beginning of a piece, an empty bar line must
be added

@lilypond[verbatim,ragged-right,quote,fragment,relative]
\set Score.currentBarNumber = #50
\bar ""
\repeat unfold 4 {c4 c c c} \break
\repeat unfold 4 {c4 c c c}
@end lilypond

Bar numbers can be typeset at regular intervals instead of at the
beginning of each line.  This is illustrated in the following example,
whose source is available as
@lsr{staff,making-bar-numbers-appear-at-regular-intervals.ly}.

@lilypondfile[ragged-right,quote]{bar-number-regular-interval.ly}

Bar numbers can be removed entirely by removing the Bar number
engraver from the score.

@lilypond[verbatim,ragged-right,quote]
\layout {
  \context {
    \Score
    \remove "Bar_number_engraver"
  }
}
\relative c''{
c4 c c c \break
c4 c c c
}
@end lilypond


@seealso

Program reference: @internalsref{BarNumber}.

Examples: @lsrdir{staff}


@refbugs

Bar numbers can collide with the @internalsref{StaffGroup} bracket, if
there is one at the top.  To solve this, the
@code{padding} property of @internalsref{BarNumber} can be
used to position the number correctly.


@anchor{Barnumber check}
@unnumberedsubsubsec Barnumber check

When copying large pieces of music, it can be helpful to check that
the LilyPond bar number corresponds to the original that you are
entering from.  This can be checked with @code{\barNumberCheck}, for
example,

@verbatim
\barNumberCheck #123
@end verbatim

@noindent
will print a warning if the @code{currentBarNumber} is not 123 when it
is processed.


@anchor{Rehearsal marks}
@unnumberedsubsubsec Rehearsal marks

@cindex Rehearsal marks
@funindex \mark

To print a rehearsal mark, use the @code{\mark} command

@lilypond[quote,ragged-right,fragment,verbatim,relative=2]
c1 \mark \default
c1 \mark \default
c1 \mark #8
c1 \mark \default
c1 \mark \default
@end lilypond

@noindent
The letter@tie{}@q{I} is skipped in accordance with engraving traditions.
If you wish to include the letter @q{I}, then use

@example
\set Score.markFormatter = #format-mark-alphabet
@end example

The mark is incremented automatically if you use @code{\mark
\default}, but you can also use an integer argument to set the mark
manually.  The value to use is stored in the property
@code{rehearsalMark}.

The style is defined by the property @code{markFormatter}.  It is a
function taking the current mark (an integer) and the current context
as argument.  It should return a markup object.  In the following
example, @code{markFormatter} is set to a canned procedure.  After a
few measures, it is set to function that produces a boxed number.

@lilypond[fragment,quote,ragged-right,verbatim,relative=2]
\set Score.markFormatter = #format-mark-numbers
c1 \mark \default
c1 \mark \default
\set Score.markFormatter = #format-mark-box-numbers
c1 \mark \default
c1 \mark \default
c1
@end lilypond

The file @file{scm/@/translation@/-functions@/.scm} contains the definitions
of @code{format-mark-numbers} (the default format),
@code{format-mark-box-numbers},
@code{format-mark-letters} and @code{format-mark-box-letters}.
These can be used as inspiration for other formatting functions.

You may use @code{format-mark-barnumbers}, @code{format-mark-box-barnumbers},
and @code{format-mark-circle-barnumbers} to get bar numbers instead of
incremented numbers or letters.

Other styles of rehearsal mark can be specified manually

@example
\mark "A1"
@end example

@noindent
@code{Score.markFormatter} does not affect marks specified in this manner.
However, it is possible to apply a @code{\markup} to the string.

@example
\mark \markup@{ \box A1 @}
@end example

@cindex segno
@cindex coda
@cindex D.S al Fine

Music glyphs (such as the segno sign) may be printed inside
a @code{\mark}

@lilypond[fragment,quote,ragged-right,verbatim,relative]
c1 \mark \markup { \musicglyph #"scripts.segno" }
c1 \mark \markup { \musicglyph #"scripts.coda" }
c1 \mark \markup { \musicglyph #"scripts.ufermata" }
c1
@end lilypond

@noindent
See @ref{The Feta font}, for a list of symbols which may be
printed with @code{\musicglyph}.

For common tweaks to the positioning of rehearsal marks, see @ref{Text marks}.

@seealso

This manual: @ref{Text marks}.

Program reference: @internalsref{RehearsalMark}.

Init files: @file{scm/@/translation@/-functions@/.scm} contains the
definition of @code{format-mark-numbers} and
@code{format-mark-letters}.  They can be used as inspiration for other
formatting functions.

Examples: @lsr{parts,rehearsal-mark-numbers.ly}


@node Special rhythmic concerns
@subsection Special rhythmic concerns


@anchor{Grace notes}
@unnumberedsubsubsec Grace notes

@funindex \grace
@cindex ornaments
@cindex grace notes
@cindex appoggiatura
@cindex acciaccatura

Grace notes are ornaments that are written out.  The most common ones
are acciaccatura, which should be played as very short.  It is denoted
by a slurred small note with a slashed stem.  The appoggiatura is a
grace note that takes a fixed fraction of the main note, and is
denoted as a slurred note in small print without a slash.  They
are entered with the commands @code{\acciaccatura} and
@code{\appoggiatura}, as demonstrated in the following example

@lilypond[quote,ragged-right,relative=2,verbatim,fragment]
b4 \acciaccatura d8 c4 \appoggiatura e8 d4
\acciaccatura { g16[ f] } e4
@end lilypond

Both are special forms of the @code{\grace} command.  By prefixing this
keyword to a music expression, a new one is formed, which will be
printed in a smaller font and takes up no logical time in a measure.

@lilypond[quote,ragged-right,relative=2,verbatim,fragment]
c4 \grace c16 c4
\grace { c16[ d16] } c2 c4
@end lilypond

@noindent
Unlike @code{\acciaccatura} and @code{\appoggiatura}, the
@code{\grace} command does not start a slur.

@cindex timing, internal

Internally, timing for grace notes is done using a second, @q{grace}
timing.  Every point in time consists of two rational numbers: one
denotes the logical time, one denotes the grace timing.  The above
example is shown here with timing tuples

@lilypond[quote,ragged-right]
<<
  \relative c''{
    c4 \grace c16 c4 \grace {
    c16[ d16] } c2 c4
  }
  \new Lyrics \lyricmode {
    \override LyricText #'font-family = #'typewriter

    \markup { (0,0) } 4
    \grace { \markup {
      ( \fraction 1 4 , \fraction -1 16 ) } 16 }
    \markup { (\fraction 1 4 , 0 ) } 4
    \grace {
      \markup { (\fraction 2 4 , \fraction "-1" 8 ) } 16
      \markup { (\fraction 2 4 , \fraction "-1" 16 ) } 16
    }
    \markup { ( \fraction 2 4 , 0 ) }
  }
>>
@end lilypond

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

@lilypond[quote,ragged-right,relative=2,verbatim,fragment]
<< \new Staff { e4 \grace { c16[ d e f] } e4 }
   \new Staff { c4 \grace { g8[ b] } c4 } >>
@end lilypond

@funindex \afterGrace

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

@lilypond[ragged-right, verbatim,relative=2,fragment]
c1 \afterGrace d1 { c16[ d] } c4
@end lilypond

This will put the grace notes after a @q{space} lasting 3/4 of the
length of the main note.  The fraction 3/4 can be changed by setting
@code{afterGraceFraction}, ie.

@example
#(define afterGraceFraction (cons 7 8))
@end example

@noindent
will put the grace note at 7/8 of the main note.

The same effect can be achieved manually by doing

@lilypond[quote,ragged-right,fragment,verbatim,relative=2]
\new Voice {
  << { d1^\trill_( }
     { s2 \grace { c16[ d] } } >>
  c4)
}
@end lilypond

@noindent
By adjusting the duration of the skip note (here it is a half-note),
the space between the main-note and the grace is adjusted.

A @code{\grace} music expression will introduce special typesetting settings,
for example, to produce smaller type, and set directions.  Hence, when
introducing layout tweaks, they should be inside the grace expression,
for example,

@lilypond[quote,ragged-right,fragment,verbatim,relative=2]
\new Voice {
  \acciaccatura {
    \stemDown
    f16->
    \stemNeutral
  }
  g4
}
@end lilypond

@noindent
The overrides should also be reverted inside the grace expression.

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

@example
\new Staff @{
  #(add-grace-property 'Voice 'Stem 'direction '())
  @dots{}
@}
@end example

@noindent
Another option is to change the variables @code{startGraceMusic},
@code{stopGraceMusic}, @code{startAcciaccaturaMusic},
@code{stopAcciaccaturaMusic}, @code{startAppoggiaturaMusic},
@code{stopAppoggiaturaMusic}.  More information is in the file
@file{ly/@/grace@/-init@/.ly}.

@noindent
The slash through the stem in acciaccaturas can be obtained
in other situations by @code{\override Stem  #'stroke-style = #"grace"}.


@commonprop

Grace notes may be forced to use floating spacing,

@lilypond[relative=2,ragged-right]
<<
  \override Score.SpacingSpanner #'strict-grace-spacing = ##t
  \new Staff {
     c'4
     \afterGrace
     c'4
     { c'16[ c'8 c'16] }
     c'4
  }  
  \new Staff {
     c'16[ c'16 c'16 c'16]
     c'16[ c'16 c'16 c'16]
     c'4
  }
>>
@end lilypond


@seealso

Program reference: @internalsref{GraceMusic}.


@refbugs

A score that starts with a @code{\grace} expression needs an explicit
@code{\new Voice} declaration, otherwise the main note and the grace
note end up on different staves.

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,

@lilypond[quote,ragged-right,relative=2,verbatim,fragment]
<< \new Staff { e4 \bar "|:" \grace c16 d4 }
   \new Staff { c4 \bar "|:" d4 } >>
@end lilypond

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

@lilypond[quote,ragged-right,relative=2,verbatim,fragment]
<< \new Staff { e4 \bar "|:" \grace c16 d4 }
   \new Staff { c4 \bar "|:" \grace s16 d4 } >>
@end lilypond

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.


@anchor{Aligning to cadenzas}
@unnumberedsubsubsec Aligning to cadenzas

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

A solution to this problem are the functions @code{mmrest-of-length}
and @code{skip-of-length}.  These Scheme functions take a piece of music
as argument, and generate a @code{\skip} or multi-rest, exactly as
long as the piece.  The use of @code{mmrest-of-length} is demonstrated
in the following example.

@lilypond[verbatim,ragged-right,quote]
cadenza = \relative c' {
  c4 d8 << { e f g } \\ { d4. } >>
  g4 f2 g4 g
}

\new GrandStaff <<
  \new Staff { \cadenza c'4 }
  \new Staff {
    #(ly:export (mmrest-of-length cadenza))
    c'4
  }
>>
@end lilypond


@anchor{Time administration}
@unnumberedsubsubsec Time administration

@cindex Time administration

Time is administered by the @internalsref{Time_signature_engraver},
which usually lives in the @internalsref{Score} context.  The
bookkeeping deals with the following variables

@table @code
@item currentBarNumber
The measure number.

@item measureLength
The length of the measures in the current time signature.  For a 4/4
time this is@tie{}1, and for 6/8 it is 3/4.

@item measurePosition
The point within the measure where we currently are.  This quantity
is reset to@tie{}0 whenever it exceeds @code{measureLength}.  When that
happens, @code{currentBarNumber} is incremented.

@item 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.
@end table

Timing can be changed by setting any of these variables explicitly.
In the next example, the 4/4 time signature is printed, but
@code{measureLength} is set to 5/4.  After a while, the measure is
shortened by 1/8, by setting @code{measurePosition} to 7/8 at 2/4
in the measure, so the next bar line will fall at 2/4 + 3/8.  The
3/8 arises because 5/4 normally has 10/8, but we have manually
set the measure position to be 7/8 and 10/8 - 7/8 = 3/8.

@lilypond[quote,ragged-right,verbatim,relative,fragment]
\set Score.measureLength = #(ly:make-moment 5 4)
c1 c4
c1 c4
c4 c4
\set Score.measurePosition = #(ly:make-moment 7 8)
b8 b b
c4 c1
@end lilypond

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


@anchor{Proportional notation (introduction)}
@unnumberedsubsubsec Proportional notation (introduction)
@cindex Proportional notation

See @ref{Proportional notation}.


TODO: remove all this stuff?

Notes can be spaced proportionally to their time-difference by
assigning a duration to @code{proportionalNotationDuration}

@lilypond[quote,ragged-right,verbatim,relative=2,fragment]
<<
  \set Score.proportionalNotationDuration = #(ly:make-moment 1 16)
  \new Staff { c8[ c c c c c]  c4 c2 r2 }
  \new Staff { c2  \times 2/3 { c8 c c } c4 c1 }
>>
@end lilypond

Setting this property only affects the ideal spacing between
consecutive notes.  For true proportional notation, the following
settings are also required.

@itemize @bullet

@item True proportional notation requires that symbols are allowed to
overstrike each other.  That is achieved by removing the
@internalsref{Separating_line_group_engraver} from
@internalsref{Staff} context.

@item Spacing influence of  prefatory matter (clefs, bar lines, etc.)
is removed by setting the @code{strict-note-spacing} property to
@code{#t} in @internalsref{SpacingSpanner} grob.

@item Optical spacing tweaks are switched by setting 
@code{uniform-stretching} in @internalsref{SpacingSpanner} to true.


@end itemize

@seealso

Examples: @lsr{spacing,proportional@/-spacing@/.ly}, 
@lsr{spacing,proportional@/-strict@/-grace@/-notes@/.ly}, and
@lsr{spacing,proportional@/-strict@/-notespacing@/.ly}

An example of strict proportional notation is in the
example file @file{input/proportional.ly}.