version that you are working on. See TRANSLATION for details.
@end ignore
+@c \version "2.11.55"
+
@node Changing defaults
@chapter Changing defaults
+@strong{N.B. This Chapter is under heavy development at present.}
The purpose of LilyPond's design is to provide the finest output
quality as a default. Nevertheless, it may happen that you need to
@uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/user/@/lilypond@/-internals/,on@/-line},
but is also included with the LilyPond documentation package.
+@c TODO The following is at variance to what actually follows. Fix -td
+
There are four areas where the default settings may be changed:
@itemize
@item
Page layout: changing the appearance of the spacing, line
breaks, and page dimensions. These modifications are discussed
-in @ref{Non-musical notation}, and @ref{Spacing issues}.
+@c in @ref{notation}, and @ref{Spacing issues}.
@end itemize
Internally, LilyPond uses Scheme (a LISP dialect) to provide
@menu
-* Interpretation contexts::
-* The \override command::
+* Interpretation contexts::
+* Explaining the Internals Reference::
+* Modifying properties::
+* Useful concepts and properties::
+* Common properties::
+* Advanced tweaks::
+* Discussion of specific tweaks::
@end menu
This section describes what contexts are, and how to modify them.
@menu
-* Contexts explained::
-* Creating contexts::
-* Changing context properties on the fly::
-* Modifying context plug-ins::
-* Layout tunings within contexts::
-* Changing context default settings::
-* Defining new contexts::
-* Aligning contexts::
-* Vertical grouping of grobs::
+* Contexts explained::
+* Creating contexts::
+* Modifying context plug-ins::
+* Changing context default settings::
+* Defining new contexts::
+* Aligning contexts::
@end menu
@node Contexts explained
@subsection Contexts explained
-When music is printed, a lot of notational elements must be added to the
-output. For example, compare the input and output of the following example:
+@ignore
+@c TODO Rethink and rewrite
+
+>> > > - list of contexts: my *danger unmaintainable*
+>> > > alarm just went off. I'm
+
+I knew it would... And leaving out some of them is perfectly fine
+with me.
+I do think that a list like this, with the main contexts and a
+brief
+description of what they do (perhaps also with a note about what
+default
+behavior is associated with each of them, but this may be
+unmanageable),
+should be there, and then we could simply list the remaining ones
+without
+further explanation and with links to the IR.
+@end ignore
-@lilypond[quote,verbatim,relative=2,fragment]
-cis4 cis2. g4
-@end lilypond
+@c TODO Improve layout, order and consistency of wording -td
-The input is rather sparse, but in the output, bar lines, accidentals,
-clef, and time signature are added. LilyPond @emph{interprets} the
-input. During this step, the musical information is inspected in time
-order, similar to reading a score from left to right. While reading
-the input, the program remembers where measure boundaries are, and which
-pitches require explicit accidentals. This information can be presented on
-several levels. For example, the effect of an accidental is limited
-to a single staff, while a bar line must be synchronized across the
-entire score.
+@c TODO Add introduction which explains contexts in generality -td
-Within LilyPond, these rules and bits of information are grouped in
-@emph{Contexts}. Some examples of contexts are @code{Voice},
-@code{Staff}, and @code{Score}. They are hierarchical, for
-example: a @code{Staff} can contain many @code{Voice}s, and a
-@code{Score} can contain many @code{Staff} contexts.
+Contexts are arranged heirarchically:
-@quotation
-@sourceimage{context-example,5cm,,}
-@end quotation
+@menu
+* Score - the master of all contexts::
+* Top-level contexts - staff containers::
+* Intermediate-level contexts - staves::
+* Bottom-level contexts - voices::
+@end menu
-Each context has the responsibility for enforcing some notation rules,
-creating some notation objects and maintaining the associated
-properties. For example, the @code{Voice} context may introduce an
-accidental and then the @code{Staff} context maintains the rule to
-show or suppress the accidental for the remainder of the measure. The
-synchronization of bar lines is handled at @code{Score} context.
+@node Score - the master of all contexts
+@unnumberedsubsubsec Score - the master of all contexts
-However, in some music we may not want the bar lines to be
-synchronized -- consider a polymetric score in 4/4 and 3/4 time. In
-such cases, we must modify the default settings of the @code{Score}
-and @code{Staff} contexts.
+This is the top level notation context. No other context can
+contain a Score context. By default the Score context handles
+the administration of time signatures and makes sure that items
+such as clefs, time signatures, and key-signatures are aligned
+across staves.
-For very simple scores, contexts are created implicitly, and you need
-not be aware of them. For larger pieces, such as anything with more
-than one staff, they must be
-created explicitly to make sure that you get as many staves as you
-need, and that they are in the correct order. For typesetting pieces
-with specialized notation, it can be useful to modify existing or
-to define new contexts.
+A Score context is instantiated implicitly when a
+@code{\score @{@dots{}@}} or @code{\layout @{@dots{}@}} block is
+processed, or explicitly when a @code{\new Score} command is
+executed.
+@node Top-level contexts - staff containers
+@unnumberedsubsubsec Top-level contexts - staff containers
-A complete description of all available contexts is in the program
-reference, see
-@ifhtml
-@internalsref{Contexts}.
-@end ifhtml
-@ifnothtml
-Translation @expansion{} Context.
-@end ifnothtml
+@strong{@emph{StaffGroup}}
-@c [TODO: describe propagation]
+Groups staves while adding a bracket on the left side, grouping
+the staves together. The bar lines of the contained staves are
+connected vertically. StaffGroup only consists of a collection
+of staves, with a bracket in front and spanning bar lines.
+
+@strong{@emph{ChoirStaff}}
+
+Identical to StaffGroup except that the bar lines of the contained
+staves are not connected vertically.
+
+@strong{@emph{GrandStaff}}
+
+A group of staves, with a brace on the left side, grouping
+the staves together. The bar lines of the contained staves are
+connected vertically.
+
+@strong{@emph{PianoStaff}}
+
+TODO No longer correct? Check. -td
+
+Just like GrandStaff but with a forced distance between the
+staves, so cross staff beaming and slurring can be used.
+
+@strong{@emph{InnerStaffGroup}}
+
+TODO -td
+
+@strong{@emph{InnerChoirStaff}}
+
+TODO -td
+
+@node Intermediate-level contexts - staves
+@unnumberedsubsubsec Intermediate-level contexts - staves
+
+@strong{@emph{Staff}}
+
+Handles clefs, bar lines, keys, accidentals. It can contain
+Voice contexts.
+
+@strong{@emph{RhythmicStaff}}
+
+Like Staff but for printing rhythms. Pitches are ignored;
+the notes are printed on one line.
+
+@strong{@emph{TabStaff}}
+
+Context for generating tablature. By default lays the music
+expression out as a guitar tablature, printed on six lines.
+
+@strong{@emph{DrumStaff}}
+
+Handles typesetting for percussion. Can contain DrumVoice
+
+@strong{@emph{VaticanaStaff}}
+
+Same as Staff, except that it is designed for typesetting
+a piece in gregorian style.
+
+@strong{@emph{MensuralStaff}}
+
+Same as Staff, except that it is designed for typesetting
+a piece in mensural style.
+
+@node Bottom-level contexts - voices
+@unnumberedsubsubsec Bottom-level contexts - voices
+
+Voice-level contexts initialise certain properties and start
+appropriate engravers. Being bottom-level contexts, they cannot
+contain other contexts.
+
+@strong{@emph{Voice}}
+
+Corresponds to a voice on a staff. This context handles the
+conversion of dynamic signs, stems, beams, super- and sub-scripts,
+slurs, ties, and rests. You have to instantiate this explicitly
+if you require multiple voices on the same staff.
+
+@strong{@emph{VaticanaVoice}}
+
+Same as Voice, except that it is designed for typesetting a piece
+in gregorian style.
+
+@strong{@emph{MensuralVoice}}
+
+Same as Voice, with modifications for typesetting a piece in
+mensural style.
+
+@strong{@emph{Lyrics}}
+
+Corresponds to a voice with lyrics. Handles the printing of a
+single line of lyrics.
+
+@strong{@emph{DrumVoice}}
+
+The voice context used in a percussion staff.
+
+@strong{@emph{FiguredBass}}
+
+The context in which BassFigure objects are created from
+input entered in @code{\figuremode} mode.
+
+@strong{@emph{TabVoice}}
+
+The voice context used within a TabStaff context. Usually left to
+be created implicitly.
+
+@strong{@emph{ChordNames}}
+
+Typesets chord names.
+
+------------------------------
+
+TODO
+
+Then the following, which I don't know what to do with:
+
+ * GregorianTranscriptionVoice
+ * GregorianTranscriptionStaff
+
+ * FretBoards
+ Engraves fretboards from chords. Not easy... Not
+documented.
+ There is now some documentation on FretBoards in the NR, under
+ instrument-specific notation -- cds.
+
+ * NoteNames
+
+ * CueVoice Not documented
+ * Global
+ Hard coded entry point for LilyPond. Cannot be tuned.
+ * Devnull
+ Silently discards all musical information given to this
+context.
@node Creating contexts
@subsection Creating contexts
+@c TODO \new Score and \score
+@c TODO more complete descriptions rather than learning style
+
For scores with only one voice and one staff, contexts are
created automatically. For more complex scores, it is necessary to
create them by hand. There are three commands that do this.
@end itemize
-@node Changing context properties on the fly
-@subsection Changing context properties on the fly
-
-@cindex properties
-@funindex \set
-@cindex changing properties
-
-Each context can have different @emph{properties}, variables contained
-in that context. They can be changed during the interpretation step.
-This is achieved by inserting the @code{\set} command in the music,
-
-@example
-\set @var{context}.@var{prop} = #@var{value}
-@end example
-
-For example,
-@lilypond[quote,verbatim,relative=2,fragment]
-R1*2
-\set Score.skipBars = ##t
-R1*2
-@end lilypond
-
-This command skips measures that have no notes. The result is that
-multi-rests are condensed. The value assigned is a Scheme object. In
-this case, it is @code{#t}, the boolean True value.
-
-If the @var{context} argument is left out, then the current bottom-most
-context (typically @code{ChordNames}, @code{Voice}, or
-@code{Lyrics}) is used. In this example,
-
-@lilypond[quote,verbatim,relative=2,fragment]
-c8 c c c
-\set autoBeaming = ##f
-c8 c c c
-@end lilypond
-
-@noindent
-the @var{context} argument to @code{\set} is left out, so automatic
-beaming is switched off in the current @internalsref{Voice}. Note that
-the bottom-most context does not always contain the property that you
-wish to change -- for example, attempting to set the @code{skipBars}
-property (of the bottom-most context, in this case @code{Voice}) will
-have no effect.
-
-@lilypond[quote,verbatim,relative=2,fragment]
-R1*2
-\set skipBars = ##t
-R1*2
-@end lilypond
-
-Contexts are hierarchical, so if a bigger context was specified, for
-example @code{Staff}, then the change would also apply to all
-@code{Voice}s in the current stave. The change is applied
-@q{on-the-fly}, during the music, so that the setting only affects the
-second group of eighth notes.
-
-@funindex \unset
-
-There is also an @code{\unset} command,
-@example
-\unset @var{context}.@var{prop}
-@end example
-
-@noindent
-which removes the definition of @var{prop}. This command removes
-the definition only if it is set in @var{context}, so
-
-@example
-\set Staff.autoBeaming = ##f
-@end example
-
-@noindent
-introduces a property setting at @code{Staff} level. The setting also
-applies to the current @code{Voice}. However,
-
-@example
-\unset Voice.autoBeaming
-@end example
-
-@noindent
-does not have any effect. To cancel this setting, the @code{\unset}
-must be specified on the same level as the original @code{\set}. In
-other words, undoing the effect of @code{Staff.autoBeaming = ##f}
-requires
-@example
-\unset Staff.autoBeaming
-@end example
-
-Like @code{\set}, the @var{context} argument does not have to be
-specified for a bottom context, so the two statements
-
-@example
-\set Voice.autoBeaming = ##t
-\set autoBeaming = ##t
-@end example
-
-@noindent
-are equivalent.
-
-
-@cindex \once
-Settings that should only apply to a single time-step can be entered
-with @code{\once}, for example in
-
-@lilypond[quote,verbatim,relative=2,fragment]
-c4
-\once \set fontSize = #4.7
-c4
-c4
-@end lilypond
-
-the property @code{fontSize} is unset automatically after the second
-note.
-
-A full description of all available context properties is in the
-program reference, see
-@ifhtml
-@internalsref{Tunable context properties}.
-@end ifhtml
-@ifnothtml
-Translation @expansion{} Tunable context properties.
-@end ifnothtml
-
-
@node Modifying context plug-ins
@subsection Modifying context plug-ins
+@c TODO Should this be Modifying engravers or Modifying contexts?
+
Notation contexts (like @code{Score} and @code{Staff}) not only
store properties,
they also contain plug-ins called @q{engravers} that create notation
For a full a description of each plug-in, see
@ifhtml
-@internalsref{Engravers}.
+@rinternals{Engravers and Performers}.
@end ifhtml
@ifnothtml
Internals Reference @expansion{} Translation @expansion{} Engravers.
@end ifnothtml
Every context described in
@ifhtml
-@internalsref{Contexts}
+@rinternals{Contexts}
@end ifhtml
@ifnothtml
Internals Reference @expansion{} Translation @expansion{} Context.
In the second staff there are no time signature or clef symbols. This
is a rather crude method of making objects disappear since it will affect
the entire staff. This method also influences the spacing, which may or
-may not be desirable. A more
-sophisticated method of blanking objects is shown in @rlearning{Common tweaks}.
+may not be desirable. More sophisticated methods of blanking objects
+are shown in @rlearning{Visibility and color of objects}.
The next example shows a practical application. Bar lines and time
signatures are normally synchronized across the score. This is done
by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
This plug-in keeps an administration of time signature, location
-within the measure, etc. By moving thes engraver from @code{Score} to
+within the measure, etc. By moving these engraver from @code{Score} to
@code{Staff} context, we can have a score where each staff has its own
time signature.
@end lilypond
-@node Layout tunings within contexts
-@subsection Layout tunings within contexts
-
-Each context is responsible for creating certain types of graphical
-objects. The settings used for printing these objects are also stored by
-context. By changing these settings, the appearance of objects can be
-altered.
+@node Changing context default settings
+@subsection Changing context default settings
-The syntax for this is
+The adjustments of the previous subsections (
+@ref{The \set command}, @ref{Modifying context plug-ins}, and
+@ref{Overview of modifying properties}) can also be entered
+separately from the music in the @code{\layout} block,
@example
-\override @var{context}.@var{name} #'@var{property} = #@var{value}
-@end example
+\layout @{
+ @dots{}
+ \context @{
+ \Staff
-Here @var{name} is the name of a graphical object, like @code{Stem} or
-@code{NoteHead}, and @var{property} is an internal variable of the
-formatting system (@q{grob property} or @q{layout property}). The latter is a
-symbol, so it must be quoted. The subsection @ref{Constructing a
-tweak}, explains what to fill in for @var{name}, @var{property}, and
-@var{value}. Here we only discuss the functionality of this command.
+ \set fontSize = #-2
+ \override Stem #'thickness = #4.0
+ \remove "Time_signature_engraver"
+ @}
+@}
+@end example
-The command
+The @code{\Staff} command brings in the existing definition of the
+staff context so that it can be modified.
-@verbatim
-\override Staff.Stem #'thickness = #4.0
-@end verbatim
-
-@noindent
-makes stems thicker (the default is 1.3, with staff line thickness as a
-unit). Since the command specifies @code{Staff} as context, it only
-applies to the current staff. Other staves will keep their normal
-appearance. Here we see the command in action:
-
-@lilypond[quote,verbatim,relative=2,fragment]
-c4
-\override Staff.Stem #'thickness = #4.0
-c4
-c4
-c4
-@end lilypond
-
-The @code{\override} command changes the definition of the @code{Stem}
-within the current @code{Staff}. After the command is interpreted
-all stems are thickened.
-
-Analogous to @code{\set}, the @var{context} argument may be left out,
-causing the default context @code{Voice} to be used. Adding
-@code{\once} applies the change during one timestep only.
-
-@lilypond[quote,fragment,verbatim,relative=2]
-c4
-\once \override Stem #'thickness = #4.0
-c4
-c4
-@end lilypond
-
-The @code{\override} must be done before the object is
-started. Therefore, when altering @emph{Spanner} objects such as slurs
-or beams, the @code{\override} command must be executed at the moment
-when the object is created. In this example,
-
-@lilypond[quote,fragment,verbatim,relative=2]
-\override Slur #'thickness = #3.0
-c8[( c
-\override Beam #'thickness = #0.6
-c8 c])
-@end lilypond
-
-@noindent
-the slur is fatter but the beam is not. This is because the command for
-@code{Beam} comes after the Beam is started, so it has no effect.
-
-Analogous to @code{\unset}, the @code{\revert} command for a context
-undoes an @code{\override} command; like with @code{\unset}, it only
-affects settings that were made in the same context. In other words, the
-@code{\revert} in the next example does not do anything.
-
-@example
-\override Voice.Stem #'thickness = #4.0
-\revert Staff.Stem #'thickness
-@end example
-
-Some tweakable options are called @q{subproperties} and reside inside
-properties. To tweak those, use commands of the form
-
-@c leave this as a long long
-@example
-\override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
-@end example
-
-@noindent
-such as
-
-@example
-\override Stem #'details #'beamed-lengths = #'(4 4 3)
-@end example
-
-
-@seealso
-
-Internals: @internalsref{OverrideProperty}, @internalsref{RevertProperty},
-@internalsref{PropertySet}, @internalsref{Backend}, and
-@internalsref{All layout objects}.
-
-
-@knownissues
-
-The back-end is not very strict in type-checking object properties.
-Cyclic references in Scheme values for properties can cause hangs
-or crashes, or both.
-
-
-@node Changing context default settings
-@subsection Changing context default settings
-
-The adjustments of the previous subsections (@ref{Changing context
-properties on the fly}, @ref{Modifying context plug-ins}, and
-@ref{Layout tunings within contexts}) can also be entered separately
-from the music in the @code{\layout} block,
-
-@example
-\layout @{
- @dots{}
- \context @{
- \Staff
-
- \set fontSize = #-2
- \override Stem #'thickness = #4.0
- \remove "Time_signature_engraver"
- @}
-@}
-@end example
-
-The @code{\Staff} command brings in the existing definition of the
-staff context so that it can be modified.
-
-The statements
-@example
-\set fontSize = #-2
-\override Stem #'thickness = #4.0
-\remove "Time_signature_engraver"
-@end example
+The statements
+@example
+\set fontSize = #-2
+\override Stem #'thickness = #4.0
+\remove "Time_signature_engraver"
+@end example
@noindent
affect all staves in the score. Other contexts can be modified
@}
@end example
+TODO: add \with in here.
+
+
@node Defining new contexts
@subsection Defining new contexts
squashedPosition = #0
@end example
-The @internalsref{Pitch_squash_engraver} modifies note heads (created
-by @internalsref{Note_heads_engraver}) and sets their vertical
+The @rinternals{Pitch_squash_engraver} modifies note heads (created
+by @rinternals{Note_heads_engraver}) and sets their vertical
position to the value of @code{squashedPosition}, in this case@tie{}@code{0},
the center line.
All these plug-ins have to cooperate, and this is achieved with a
special plug-in, which must be marked with the keyword @code{\type}.
-This should always be @internalsref{Engraver_group},
+This should always be @rinternals{Engraver_group},
@example
\type "Engraver_group"
@node Aligning contexts
@subsection Aligning contexts
-New contexts may be aligned above or below exisiting contexts. This
+New contexts may be aligned above or below existing contexts. This
could be useful in setting up a vocal staff (@rlearning{Vocal ensembles}) and
in ossia,
-FIXME: this section doens't work in pdf. (?)
+@c TODO Better example needed. Ref LM, and expand on it.
@cindex ossia
@findex alignAboveContext
@end lilypond
-@node Vertical grouping of grobs
-@subsection Vertical grouping of grobs
-
-The VerticalAlignment and VerticalAxisGroup grobs work together.
-VerticalAxisGroup groups together different grobs like Staff, Lyrics,
-etc. VerticalAlignment then vertically aligns the different grobs
-grouped together by VerticalAxisGroup. There is usually only one
-VerticalAlignment per score but every Staff, Lyrics, etc. has its own
-VerticalAxisGroup.
-
+@node Explaining the Internals Reference
+@section Explaining the Internals Reference
-@node The \override command
-@section The @code{\override} command
-
-In the previous section, we have already touched on a command that
-changes layout details: the @code{\override} command. In this section,
-we will look in more detail at how to use the command in practice. The
-general syntax of this command is:
-
-@example
-\override @var{context}.@var{layout_object} #'@var{layout_property} = #@var{value}
-@end example
-
-This will set the @var{layout_property} of the specified @var{layout_object},
-which is a member of the @var{context}, to the @var{value}.
@menu
-* Constructing a tweak::
-* Navigating the program reference::
-* Layout interfaces::
-* Determining the grob property::
-* Objects connected to the input::
-* Using Scheme code instead of \tweak::
-* \set versus \override::
-* Difficult tweaks::
+* Navigating the program reference::
+* Layout interfaces::
+* Determining the grob property::
+* Naming conventions::
@end menu
-
-
-@node Constructing a tweak
-@subsection Constructing a tweak
-
-Commands which change output generally look like
-
-@example
-\override Voice.Stem #'thickness = #3.0
-@end example
-
-@noindent
-To construct this tweak we must determine these bits of information:
-
-@itemize
-@item the context: here @code{Voice}.
-@item the layout object: here @code{Stem}.
-@item the layout property: here @code{thickness}.
-@item a sensible value: here @code{3.0}.
-@end itemize
-
-Some tweakable options are called @q{subproperties} and reside inside
-properties. To tweak those, use commands in the form
-
-@example
-\override Stem #'details #'beamed-lengths = #'(4 4 3)
-@end example
-
-@cindex internal documentation
-@cindex finding graphical objects
-@cindex graphical object descriptions
-@cindex tweaking
-@funindex \override
-@cindex internal documentation
-
-For many properties, regardless of the data type of the property, setting the
-property to false ( @code{##f} ) will result in turning it off, causing
-Lilypond to ignore that property entirely. This is particularly useful for
-turning off grob properties which may otherwise be causing problems.
-
-We demonstrate how to glean this information from the notation manual
-and the program reference.
-
-
-
-
@node Navigating the program reference
@subsection Navigating the program reference
+@c TODO remove this (it's in the LM)
+@c Replace with more factual directions
+
Suppose we want to move the fingering indication in the fragment
below:
@ref{Fingering instructions}), you will notice:
@quotation
-@seealso
+@strong{See also}
-Internals Reference: @internalsref{Fingering}.
+Internals Reference: @rinternals{Fingering}.
@end quotation
forward. For example, it says
@quotation
-Accepted by: @internalsref{Fingering_engraver},
+Accepted by: @rinternals{Fingering_engraver},
@end quotation
@noindent
plug-in, which says
@quotation
-This engraver creates the following layout objects: @internalsref{Fingering}.
+This engraver creates the following layout objects: @rinternals{Fingering}.
@end quotation
In other words, once the @code{FingerEvent}s are interpreted, the
@c I can't figure out what this is supposed to mean. -gp
The @code{Fingering_engraver} is also listed to create
-@internalsref{Fingering} objects,
+@rinternals{Fingering} objects,
@c old info? it doesn't make any sense to me with our current docs.
This is also the
The programmer's reference is available as an HTML document. It is
highly recommended that you read it in HTML form, either online or
by downloading the HTML documentation. This section will be much more
-difficult to understand if you are using the
+difficult to understand if you are using the
PDF manual.
@end ifnothtml
-Follow the link to @internalsref{Fingering}. At the top of the
+Follow the link to @rinternals{Fingering}. At the top of the
page, you will see
@quotation
-Fingering objects are created by: @internalsref{Fingering_engraver} and
-@internalsref{New_fingering_engraver}.
+Fingering objects are created by: @rinternals{Fingering_engraver} and
+@rinternals{New_fingering_engraver}.
@end quotation
By following related links inside the program reference, we can follow the
@itemize
-@item @internalsref{Fingering}:
-@internalsref{Fingering} objects are created by:
-@internalsref{Fingering_engraver}
+@item @rinternals{Fingering}:
+@rinternals{Fingering} objects are created by:
+@rinternals{Fingering_engraver}
-@item @internalsref{Fingering_engraver}:
-Music types accepted: @internalsref{fingering-event}
+@item @rinternals{Fingering_engraver}:
+Music types accepted: @rinternals{fingering-event}
-@item @internalsref{fingering-event}:
+@item @rinternals{fingering-event}:
Music event type @code{fingering-event} is in Music expressions named
-@internalsref{FingerEvent}
+@rinternals{FingerEvent}
@end itemize
This path goes against the flow of information in the program: it
The program reference can also be browsed like a normal document. It
contains chapters on
@ifhtml
-@internalsref{Music definitions},
+@rinternals{Music definitions},
@end ifhtml
@ifnothtml
@code{Music definitions}
@end ifnothtml
-on @internalsref{Translation}, and the @internalsref{Backend}. Every
+on @rinternals{Translation}, and the @rinternals{Backend}. Every
chapter lists all the definitions used and all properties that may be
tuned.
@cindex grob
The HTML page that we found in the previous section describes the
-layout object called @internalsref{Fingering}. Such an object is a
+layout object called @rinternals{Fingering}. Such an object is a
symbol within the score. It has properties that store numbers (like
thicknesses and directions), but also pointers to related objects. A
layout object is also called a @emph{Grob}, which is short for Graphical
-Object. For more details about Grobs, see @internalsref{grob-interface}.
+Object. For more details about Grobs, see @rinternals{grob-interface}.
The page for @code{Fingering} lists the definitions for the
@code{Fingering} object. For example, the page says
@end itemize
Each of these aspects is captured in so-called @emph{interface}s,
-which are listed on the @internalsref{Fingering} page at the bottom
+which are listed on the @rinternals{Fingering} page at the bottom
@quotation
This object supports the following interfaces:
-@internalsref{item-interface},
-@internalsref{self-alignment-interface},
-@internalsref{side-position-interface}, @internalsref{text-interface},
-@internalsref{text-script-interface}, @internalsref{font-interface},
-@internalsref{finger-interface}, and @internalsref{grob-interface}.
+@rinternals{item-interface},
+@rinternals{self-alignment-interface},
+@rinternals{side-position-interface}, @rinternals{text-interface},
+@rinternals{text-script-interface}, @rinternals{font-interface},
+@rinternals{finger-interface}, and @rinternals{grob-interface}.
@end quotation
Clicking any of the links will take you to the page of the respective
We have been talking of @emph{the} @code{Fingering} object, but actually it
does not amount to much. The initialization file (see
-@rlearning{Default files})
+@rlearning{Other sources of information})
@file{scm/@/define@/-grobs@/.scm} shows the soul of the @q{object},
@example
@node Determining the grob property
@subsection Determining the grob property
+@c TODO remove this (it's in the LM)
+@c Replace with more factual directions
+
Recall that we wanted to change the position of the @b{2} in
@lilypond[quote,fragment,relative=2,verbatim]
In this case, the context for this tweak is @code{Voice}. This
fact can also be deduced from the program reference, for the page for
-the @internalsref{Fingering_engraver} plug-in says
+the @rinternals{Fingering_engraver} plug-in says
@quotation
-Fingering_engraver is part of contexts: @dots{} @internalsref{Voice}
+Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
@end quotation
-@node Objects connected to the input
-@subsection Objects connected to the input
-
-@funindex \tweak
-
-In some cases, it is possible to take a short-cut for tuning graphical
-objects. For objects that result directly from a piece of the input,
-you can use the @code{\tweak} function, for example
-
-@lilypond[relative=2,fragment,verbatim,ragged-right]
-<
- c
- \tweak #'color #red d
- g
- \tweak #'duration-log #1 a
->4-\tweak #'padding #10 -.
-@end lilypond
+@node Naming conventions
+@subsection Naming conventions
-As you can see, properties are set in the objects directly,
-without mentioning the grob name or context where this should be
-applied.
+Another thing that is needed, is an overview of the various naming
+conventions:
-This technique only works for objects that are directly connected to
-an @internalsref{Event} from the input, for example
+ scheme functions: lowercase-with-hyphens (incl. one-word
+names)
+ scheme functions: ly:plus-scheme-style
+ music events, music classes and music properties:
+as-scheme-functions
+ Grob interfaces: scheme-style
+ backend properties: scheme-style (but X and Y!)
+ contexts (and MusicExpressions and grobs): Capitalized or
+CamelCase
+ context properties: lowercaseFollowedByCamelCase
+ engravers:
+Capitalized_followed_by_lowercase_and_with_underscores
-@itemize
-@item note heads, caused by chord-pitch (i.e., notes inside a chord)
-@item articulation signs, caused by articulation instructions
-@end itemize
+Which of these are conventions and which are rules?
+Which are rules of the underlying language, and which are
+LP-specific?
-It notably does not work for stems and accidentals (these are caused
-by note heads, not by music events) or clefs (these are not caused by
-music inputs, but rather by the change of a property value).
-There are very few objects which are @emph{directly} connected to
-output. A normal note (like @code{c4}) is not directly connected
-to output, so
+@node Modifying properties
+@section Modifying properties
-@example
-\tweak #'color #red c4
-@end example
+@menu
+* Overview of modifying properties::
+* The \set command::
+* The \override command::
+* \set versus \override::
+* Objects connected to the input::
+@end menu
-@noindent
-does not change color. See @ref{Displaying music expressions}, for
-details.
+@node Overview of modifying properties
+@subsection Overview of modifying properties
-@node Using Scheme code instead of \tweak
-@subsection Using Scheme code instead of @code{\tweak}
+Each context is responsible for creating certain types of graphical
+objects. The settings used for printing these objects are also stored by
+context. By changing these settings, the appearance of objects can be
+altered.
-The main disadvantage of @code{\tweak} is its syntactical
-inflexibility. For example, the following produces a syntax error.
+The syntax for this is
@example
-F = \tweak #'font-size #-3 -\flageolet
-
-\relative c'' @{
- c4^\F c4_\F
-@}
+\override @var{context}.@var{name} #'@var{property} = #@var{value}
@end example
-@noindent
-With other words, @code{\tweak} doesn't behave like an articulation
-regarding the syntax; in particular, it can't be attached with
-@code{^} and @code{_}.
+Here @var{name} is the name of a graphical object, like
+@code{Stem} or @code{NoteHead}, and @var{property} is an internal
+variable of the formatting system (@q{grob property} or @q{layout
+property}). The latter is a symbol, so it must be quoted. The
+subsection @ref{Modifying properties}, explains what to fill in
+for @var{name}, @var{property}, and @var{value}. Here we only
+discuss the functionality of this command.
-Using Scheme, this problem can be circumvented. The route to the
-result is given in @ref{Adding articulation to notes (example)},
-especially how to use @code{\displayMusic} as a helping guide.
+The command
-@example
-F = #(let ((m (make-music 'ArticulationEvent
- 'articulation-type "flageolet")))
- (set! (ly:music-property m 'tweaks)
- (acons 'font-size -3
- (ly:music-property m 'tweaks)))
- m)
-
-\relative c'' @{
- c4^\F c4_\F
-@}
-@end example
+@verbatim
+\override Staff.Stem #'thickness = #4.0
+@end verbatim
@noindent
-Here, the @code{tweaks} properties of the flageolet object
-@code{m} (created with @code{make-music}) are extracted with
-@code{ly:music-property}, a new key-value pair to change the
-font size is prepended to the property list with the
-@code{acons} Scheme function, and the result is finally
-written back with @code{set!}. The last element of the
-@code{let} block is the return value, @code{m} itself.
+makes stems thicker (the default is 1.3, with staff line thickness as a
+unit). Since the command specifies @code{Staff} as context, it only
+applies to the current staff. Other staves will keep their normal
+appearance. Here we see the command in action:
+@lilypond[quote,verbatim,relative=2,fragment]
+c4
+\override Staff.Stem #'thickness = #4.0
+c4
+c4
+c4
+@end lilypond
-@node \set versus \override
-@subsection @code{\set} vs. @code{\override}
+The @code{\override} command changes the definition of the @code{Stem}
+within the current @code{Staff}. After the command is interpreted
+all stems are thickened.
-We have seen two methods of changing properties: @code{\set} and
-@code{\override}. There are actually two different kinds of
-properties.
+Analogous to @code{\set}, the @var{context} argument may be left out,
+causing the default context @code{Voice} to be used. Adding
+@code{\once} applies the change during one timestep only.
-Contexts can have properties, which are usually named in
-@code{studlyCaps}. They mostly control the translation from
-music to notatino, eg. @code{localKeySignature} (for determining
-whether to print accidentals), @code{measurePosition} (for
-determining when to print a bar line). Context properties can
-change value over time while interpreting a piece of music;
+@lilypond[quote,fragment,verbatim,relative=2]
+c4
+\once \override Stem #'thickness = #4.0
+c4
+c4
+@end lilypond
+
+The @code{\override} must be done before the object is
+started. Therefore, when altering @emph{Spanner} objects such as slurs
+or beams, the @code{\override} command must be executed at the moment
+when the object is created. In this example,
+
+@lilypond[quote,fragment,verbatim,relative=2]
+\override Slur #'thickness = #3.0
+c8[( c
+\override Beam #'thickness = #0.6
+c8 c])
+@end lilypond
+
+@noindent
+the slur is fatter but the beam is not. This is because the command for
+@code{Beam} comes after the Beam is started, so it has no effect.
+
+Analogous to @code{\unset}, the @code{\revert} command for a context
+undoes an @code{\override} command; like with @code{\unset}, it only
+affects settings that were made in the same context. In other words, the
+@code{\revert} in the next example does not do anything.
+
+@example
+\override Voice.Stem #'thickness = #4.0
+\revert Staff.Stem #'thickness
+@end example
+
+Some tweakable options are called @q{subproperties} and reside inside
+properties. To tweak those, use commands of the form
+
+@c leave this as a long long
+@example
+\override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
+@end example
+
+@noindent
+such as
+
+@example
+\override Stem #'details #'beamed-lengths = #'(4 4 3)
+@end example
+
+
+@seealso
+
+Internals: @rinternals{OverrideProperty}, @rinternals{RevertProperty},
+@rinternals{PropertySet}, @rinternals{Backend}, and
+@rinternals{All layout objects}.
+
+
+@knownissues
+
+The back-end is not very strict in type-checking object properties.
+Cyclic references in Scheme values for properties can cause hangs
+or crashes, or both.
+
+
+
+@node The \set command
+@subsection The @code{\set} command
+
+@cindex properties
+@funindex \set
+@cindex changing properties
+
+Each context can have different @emph{properties}, variables contained
+in that context. They can be changed during the interpretation step.
+This is achieved by inserting the @code{\set} command in the music,
+
+@example
+\set @var{context}.@var{prop} = #@var{value}
+@end example
+
+For example,
+@lilypond[quote,verbatim,relative=2,fragment]
+R1*2
+\set Score.skipBars = ##t
+R1*2
+@end lilypond
+
+This command skips measures that have no notes. The result is that
+multi-rests are condensed. The value assigned is a Scheme object. In
+this case, it is @code{#t}, the boolean True value.
+
+If the @var{context} argument is left out, then the current bottom-most
+context (typically @code{ChordNames}, @code{Voice}, or
+@code{Lyrics}) is used. In this example,
+
+@lilypond[quote,verbatim,relative=2,fragment]
+c8 c c c
+\set autoBeaming = ##f
+c8 c c c
+@end lilypond
+
+@noindent
+the @var{context} argument to @code{\set} is left out, so automatic
+beaming is switched off in the current @rinternals{Voice}. Note that
+the bottom-most context does not always contain the property that you
+wish to change -- for example, attempting to set the @code{skipBars}
+property (of the bottom-most context, in this case @code{Voice}) will
+have no effect.
+
+@lilypond[quote,verbatim,relative=2,fragment]
+R1*2
+\set skipBars = ##t
+R1*2
+@end lilypond
+
+Contexts are hierarchical, so if a bigger context was specified, for
+example @code{Staff}, then the change would also apply to all
+@code{Voice}s in the current stave. The change is applied
+@q{on-the-fly}, during the music, so that the setting only affects the
+second group of eighth notes.
+
+@funindex \unset
+
+There is also an @code{\unset} command,
+@example
+\unset @var{context}.@var{prop}
+@end example
+
+@noindent
+which removes the definition of @var{prop}. This command removes
+the definition only if it is set in @var{context}, so
+
+@example
+\set Staff.autoBeaming = ##f
+@end example
+
+@noindent
+introduces a property setting at @code{Staff} level. The setting also
+applies to the current @code{Voice}. However,
+
+@example
+\unset Voice.autoBeaming
+@end example
+
+@noindent
+does not have any effect. To cancel this setting, the @code{\unset}
+must be specified on the same level as the original @code{\set}. In
+other words, undoing the effect of @code{Staff.autoBeaming = ##f}
+requires
+@example
+\unset Staff.autoBeaming
+@end example
+
+Like @code{\set}, the @var{context} argument does not have to be
+specified for a bottom context, so the two statements
+
+@example
+\set Voice.autoBeaming = ##t
+\set autoBeaming = ##t
+@end example
+
+@noindent
+are equivalent.
+
+
+@cindex \once
+Settings that should only apply to a single time-step can be entered
+with @code{\once}, for example in
+
+@lilypond[quote,verbatim,relative=2,fragment]
+c4
+\once \set fontSize = #4.7
+c4
+c4
+@end lilypond
+
+the property @code{fontSize} is unset automatically after the second
+note.
+
+A full description of all available context properties is in the
+program reference, see
+@ifhtml
+@rinternals{Tunable context properties}.
+@end ifhtml
+@ifnothtml
+Translation @expansion{} Tunable context properties.
+@end ifnothtml
+
+
+
+@node The \override command
+@subsection The @code{\override} command
+
+Commands which change output generally look like
+
+@example
+\override Voice.Stem #'thickness = #3.0
+@end example
+
+@noindent
+To construct this tweak we must determine these bits of information:
+
+@itemize
+@item the context: here @code{Voice}.
+@item the layout object: here @code{Stem}.
+@item the layout property: here @code{thickness}.
+@item a sensible value: here @code{3.0}.
+@end itemize
+
+Some tweakable options are called @q{subproperties} and reside inside
+properties. To tweak those, use commands in the form
+
+@example
+\override Stem #'details #'beamed-lengths = #'(4 4 3)
+@end example
+
+@cindex internal documentation
+@cindex finding graphical objects
+@cindex graphical object descriptions
+@cindex tweaking
+@funindex \override
+@cindex internal documentation
+
+For many properties, regardless of the data type of the property, setting the
+property to false ( @code{##f} ) will result in turning it off, causing
+LilyPond to ignore that property entirely. This is particularly useful for
+turning off grob properties which may otherwise be causing problems.
+
+We demonstrate how to glean this information from the notation manual
+and the program reference.
+
+
+@node \set versus \override
+@subsection @code{\set} vs. @code{\override}
+
+We have seen two methods of changing properties: @code{\set} and
+@code{\override}. There are actually two different kinds of
+properties.
+
+Contexts can have properties, which are usually named in
+@code{studlyCaps}. They mostly control the translation from
+music to notation, eg. @code{localKeySignature} (for determining
+whether to print accidentals), @code{measurePosition} (for
+determining when to print a bar line). Context properties can
+change value over time while interpreting a piece of music;
@code{measurePosition} is an obvious example of
this. Context properties are modified with @code{\set}.
\set @var{context}.@var{name} #'@var{property} = #(cons (cons '@var{property} @var{value}) <previous value of @var{context})
@end example
-The value of @code{context} (the alist) is used to initalize
+The value of @code{context} (the alist) is used to initialize
the properties of individual grobs. Grobs also have
properties, named in Scheme style, with
@code{dashed-words}. The values of grob properties change
property (modified with @code{\set}) was created.
-@node Difficult tweaks
-@subsection Difficult tweaks
-
-There are a few classes of difficult adjustments.
+@node Objects connected to the input
+@subsection Objects connected to the input
-@itemize
+TODO: can't use \tweak in a variable
+@funindex \tweak
-@item
-One type of difficult adjustment is the appearance of spanner objects,
-such as slur and tie. Initially, only one of these objects is created,
-and they can be adjusted with the normal mechanism. However, in some
-cases the spanners cross line breaks. If this happens, these objects
-are cloned. A separate object is created for every system that it is
-in. These are clones of the original object and inherit all
-properties, including @code{\override}s.
+In some cases, it is possible to take a short-cut for tuning graphical
+objects. For objects that result directly from a piece of the input,
+you can use the @code{\tweak} function, for example
+@lilypond[relative=2,fragment,verbatim,ragged-right]
+<
+ c
+ \tweak #'color #red d
+ g
+ \tweak #'duration-log #1 a
+>4-\tweak #'padding #10 -.
+@end lilypond
-In other words, an @code{\override} always affects all pieces of a
-broken spanner. To change only one part of a spanner at a line break,
-it is necessary to hook into the formatting process. The
-@code{after-line-breaking} callback contains the Scheme procedure that
-is called after the line breaks have been determined, and layout
-objects have been split over different systems.
+As you can see, properties are set in the objects directly,
+without mentioning the grob name or context where this should be
+applied.
-In the following example, we define a procedure
-@code{my-callback}. This procedure
+This technique only works for objects that are directly connected to
+an @rinternals{Event} from the input, for example
@itemize
-@item
-determines if we have been split across line breaks
-@item
-if yes, retrieves all the split objects
-@item
-checks if we are the last of the split objects
-@item
-if yes, it sets @code{extra-offset}.
+@item note heads, caused by chord-pitch (i.e., notes inside a chord)
+@item articulation signs, caused by articulation instructions
@end itemize
-This procedure is installed into @internalsref{Tie}, so the last part
-of the broken tie is translated up.
+It notably does not work for stems and accidentals (these are caused
+by note heads, not by music events) or clefs (these are not caused by
+music inputs, but rather by the change of a property value).
+
+There are very few objects which are @emph{directly} connected to
+output. A normal note (like @code{c4}) is not directly connected
+to output, so
+
+@example
+\tweak #'color #red c4
+@end example
+
+@noindent
+does not change color. See @ref{Displaying music expressions}, for
+details.
-@lilypond[quote,verbatim,ragged-right]
-#(define (my-callback grob)
- (let* (
- ; have we been split?
- (orig (ly:grob-original grob))
- ; if yes, get the split pieces (our siblings)
- (siblings (if (ly:grob? orig)
- (ly:spanner-broken-into orig) '() )))
+@node Useful concepts and properties
+@section Useful concepts and properties
- (if (and (>= (length siblings) 2)
- (eq? (car (last-pair siblings)) grob))
- (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
-\relative c'' {
- \override Tie #'after-line-breaking =
- #my-callback
- c1 ~ \break c2 ~ c
+@menu
+* Input modes::
+* Direction and placement::
+* Distances and measurements::
+* Spanners::
+@end menu
+
+@node Input modes
+@subsection Input modes
+
+The way in which the notation contained within an input file is
+interpreted is determined by the current input mode.
+
+@strong{Chord mode}
+
+This is activated with the @code{\chordmode} command, and causes
+input to be interpreted with the syntax of chord notation, see
+@ref{Chord notation}. Chords are rendered as notes on a staff.
+
+Chord mode is also activated with the @code{\chords} command.
+This also creates a new @code{ChordNames} context and
+causes the following input to be interpreted with the syntax of
+chord notation and rendered as chord names in the @code{ChordNames}
+context, see @ref{Printing chord names}.
+
+@strong{Drum mode}
+
+This is activated with the @code{\drummode} command, and causes
+input to be interpreted with the syntax of drum notation, see
+@ref{Basic percussion notation}.
+
+Drum mode is also activated with the @code{\drums} command.
+This also creates a new @code{DrumStaff} context and causes the
+following input to be interpreted with the syntax of drum notation
+and rendered as drum symbols on a drum staff, see @ref{Basic
+percussion notation}.
+
+@strong{Figure mode}
+
+This is activated with the @code{\figuremode} command, and causes
+input to be interpreted with the syntax of figured bass, see
+@ref{Entering figured bass}.
+
+Figure mode is also activated with the @code{\figures} command.
+This also creates a new @code{FiguredBass} context and causes the
+following input to be interpreted with the figured bass syntax
+and rendered as figured bass symbols in the @code{FiguredBass}
+context, see @ref{Introduction to figured bass}.
+
+@strong{Fret and tab modes}
+
+There are no special input modes for entering fret and tab symbols.
+
+To create tab diagrams, enter notes or chords in note mode and
+render them in a @code{TabStaff} context, see
+@ref{Default tablatures}.
+
+To create fret diagrams above a staff, you have two choices.
+You can either use the @code{FretBoards} context (see
+@ref{Automatic fret diagrams} or you can enter them as a markup
+above the notes using the @code{\fret-diagram} command (see
+@ref{Fret diagram markups}).
+
+@strong{Lyrics mode}
+
+This is activated with the @code{\lyricmode} command, and causes
+input to be interpreted as lyric syllables with optional durations
+and associated lyric modifiers, see @ref{Vocal music}.
+
+Lyric mode is also activated with the @code{\addlyrics} command.
+This also creates a new @code{Lyrics} context and an implicit
+@code{\lyricsto} command which associates the following lyrics
+with the preceding music.
+
+@strong{Markup mode}
+
+This is activated with the @code{\markup} command, and causes
+input to be interpreted with the syntax of markup, see
+@ref{Text markup commands}.
+
+@c silly work-around for texinfo broken-ness
+@c (@strong{Note...} causes a spurious cross-reference in Info)
+@b{Note mode}
+
+This is the default mode or it may be activated with the
+@code{\notemode} command. Input is interpreted as pitches,
+durations, markup, etc and typeset as musical notation on a staff.
+
+It is not normally necessary to specify note mode explicitly, but
+it may be useful to do so in certain situations, for example if you
+are in lyric mode, chord mode or any other mode and want to insert
+something that only can be done with note mode syntax.
+
+For example, to indicate dynamic markings for the verses of a
+choral pieces it is necessary to enter note mode to interpret
+the markings:
+
+@lilypond[verbatim,relative=2,quote]
+{ c4 c4 c4 c4 }
+\addlyrics {
+ \notemode{\set stanza = \markup{ \dynamic f 1. } }
+ To be sung loudly
+}
+\addlyrics {
+ \notemode{\set stanza = \markup{ \dynamic p 2. } }
+ To be sung quietly
}
@end lilypond
+
+
+@node Direction and placement
+@subsection Direction and placement
+
+In typesetting music the direction and placement of many items is
+a matter of choice. For example, the stems of notes can
+be directed up or down; lyrics, dynamics, and other expressive
+marks may be placed above or below the staff; text may be aligned
+left, right or center; etc. Most of these choices may be left to
+be determined automatically by LilyPond, but in some cases it may
+be desirable to force a particular direction or placement.
+
+@strong{Default actions}
+
+By default some directions are always up or always down (e.g.
+dynamics or fermata), while other things can alternate between
+up or down based on the stem direction (like slurs or accents).
+
+@c TODO Add table showing these
+
+@strong{Context layout}
+
+Contexts are positioned in a system from top to bottom in the
+order in which they are encountered. Note, however, that a
+context will be created implicitly if a command is encountered
+when there is no suitable context available to contain it.
+
+@c TODO Add example ?
+
+The default order in which contexts are laid out can be changed,
+see @ref{Aligning contexts}
+
+@strong{Articulation direction indicators}
+
+When adding articulations to notes the direction indicator,
+@code{^} (meaning @qq{up}), @code{_} (meaning @qq{down}) or
+@code{-} (meaning @qq{use default direction}), can usually be
+omitted, in which case @code{-} is assumed. But a direction
+indicator is @strong{always} required before
+
+@itemize
+@item @code{\tweak} commands
+@item @code{\markup} commands
+@item @code{\tag} commands
+@item string markups, e.g. -"string"
+@item fingering instructions, e.g. @code{-1}
+@item articulation shortcuts, e.g. @code{-.}, @code{->}, @code{--}
+@end itemize
+
+@strong{The direction property}
+
+The position or direction of many layout objects is controlled
+by the @code{direction} property.
+
+The value of the @code{direction} property may be
+set to @code{1}, meaning @qq{up} or @qq{above}, or to @code{-1},
+meaning @qq{down} or @qq{below}. The symbols @code{UP} and
+@code{DOWN} may be used instead of @code{1} and @code{-1}
+respectively. The default direction may be specified by setting
+@code{direction} to @code{0} or @code{CENTER}. Alternatively,
+in many cases predefined commands
+exist to specify the direction. These are all of the form
+
@noindent
-When applying this trick, the new @code{after-line-breaking} callback
-should also call the old one @code{after-line-breaking}, if there is
-one. For example, if using this with @code{Hairpin},
-@code{ly:hairpin::after-line-breaking} should also be called.
+@code{\xxxUp}, @code{xxxDown}, @code{xxxNeutral}
+@noindent
+where @code{xxxNeutral} means @qq{use the default direction}.
+See @rlearning{Within-staff objects}.
-@item Some objects cannot be changed with @code{\override} for
-technical reasons. Examples of those are @code{NonMusicalPaperColumn}
-and @code{PaperColumn}. They can be changed with the
-@code{\overrideProperty} function, which works similar to @code{\once
-\override}, but uses a different syntax.
+In a few cases, arpeggio being the only common example, the value
+of the @code{direction} property specifies whether the object
+is to be placed to the right or left of the parent object. In
+this case @code{-1} or @code{LEFT} means @qq{to the left} and
+@code{1} or @code{RIGHT} means @qq{to the right}. @code{0}
+or @code{CENTER} means @qq{use the default} direction, as before.
-@example
-\overrideProperty
-#"Score.NonMusicalPaperColumn" % Grob name
-#'line-break-system-details % Property name
-#'((next-padding . 20)) % Value
-@end example
+@ignore
+These all have side-axis set to #X
+AmbitusAccidental - direction has no effect
+Arpeggio - works
+StanzaNumber - not tried
+TrillPitchAccidental - not tried
+TrillPitchGroup - not tried
+@end ignore
+
+
+
+@node Distances and measurements
+@subsection Distances and measurements
+
+DISCUSS after working on other sections.
+
+TODO: staff spaces. Maybe move into tweaks?
+
+
+@node Spanners
+@subsection Spanners
+
+Many objects of musical notation extend over several notes or even
+several bars. Examples are crescendi, trills, tuplet brackets, and
+volta repeat brackets. Such objects are called @qq{spanners}, and
+have special properties to control their appearance and behaviour.
+Some of these properties are common to all spanners; others are
+restricted to a sub-set of the spanners.
+
+@node Common properties
+@section Common properties
+
+@menu
+* Controlling visibility of objects::
+* Line styles::
+* Rotating objects::
+* Aligning objects::
+@end menu
+
+@c TODO Add new subsection Shapes of objects
+@c which would include Slur shapes
+@c with a Known issue: can't modify shapes with 'control-points if there are
+@c more than one at the same musical moment
+
+@node Controlling visibility of objects
+@subsection Controlling visibility of objects
+
+@cindex objects, visibility of
+@cindex grobs, visibility of
+@cindex visibility of objects
+
+There are four main ways in which the visibility of layout objects
+can be controlled: their stencil can be removed, they can be made
+transparent, they can be colored white, or their
+@code{break-visibility} property can be overridden. The first
+three apply to all layout objects; the last to just a few -- the
+@emph{breakable} objects. The Learning Manual introduces these
+four techniques, see @rlearning{Visibility and color of objects}.
+
+There are also a few other techniques which are specific to
+certain layout objects. These are covered under Special
+considerations.
+
+@menu
+* Removing the stencil::
+* Making objects transparent::
+* Painting objects white::
+* Using break-visibility::
+* Special considerations::
+@end menu
+
+
+@node Removing the stencil
+@unnumberedsubsubsec Removing the stencil
+
+@cindex stencil, removing
+
+Every layout object has a stencil property. By default this is set
+to the specific function which draws that object. If this property
+is overridden to @code{#f} no function will be called and the object
+will not be drawn. The default action can be recovered with
+@code{\revert}.
+
+@lilypond[quote,verbatim,relative=1]
+a1 a
+\override Score.BarLine #'stencil = ##f
+a a
+\revert Score.BarLine #'stencil
+a a a
+@end lilypond
+
+@node Making objects transparent
+@unnumberedsubsubsec Making objects transparent
+
+@cindex transparent, making objects
-Note, however, that @code{\override}, applied to
-@code{NoteMusicalPaperColumn} and @code{PaperColumn}, still works as
-expected within @code{\context} blocks.
+Every layout object has a transparent property which by default is
+set to @code{#f}. If set to @code{#t} the object still occupies
+space but is made invisible.
+@lilypond[quote,verbatim,relative=2]
+a4 a
+\once \override NoteHead #'transparent = ##t
+a a
+@end lilypond
+
+@node Painting objects white
+@unnumberedsubsubsec Painting objects white
+
+@cindex objects, coloring
+@cindex coloring objects
+@cindex layers
+@cindex printing order
+@cindex overwriting objects
+@cindex objects, overwriting
+@cindex grobs, overwriting
+
+Every layout object has a color property which by default is set
+to @code{black}. If this is overridden to @code{white} the object
+will be indistinguishable from the white background. However,
+if the object crosses other objects the color of the crossing
+points will be determined by the order in which they are drawn,
+and this may leave a ghostly image of the white object, as shown
+here:
+
+@lilypond[quote,verbatim,relative=2]
+\override Staff.Clef #'color = #white
+a1
+@end lilypond
+
+This may be avoided by changing the order of printing the objects.
+All layout objects have a @code{layer} property which should be set
+to an integer. Objects with the lowest value of @code{layer} are
+drawn first, then objects with progressively higher values are drawn,
+so objects with higher values overwrite objects with lower values.
+By default most objects are assigned a @code{layer} value of
+@code{1}, although a few objects, including @code{StaffSymbol} and
+@code{BarLine}, are assigned a value of @code{0}. The order of
+printing objects with the same value of @code{layer} is indeterminate.
+
+In the example above the white clef, with a default @code{layer}
+value of @code{1}, is drawn after the staff lines (default
+@code{layer} value @code{0}), so overwriting them. To change this,
+the @code{Clef} object must be given in a lower value of
+@code{layer}, say @code{-1}, so that it is drawn earlier:
+
+@lilypond[quote,verbatim,relative=2]
+\override Staff.Clef #'color = #white
+\override Staff.Clef #'layer = #-1
+a1
+@end lilypond
+
+@node Using break-visibility
+@unnumberedsubsubsec Using break-visibility
+
+@c TODO Add making other objects breakable
+
+@cindex break-visibility
+
+Most layout objects are printed only once, but some like
+bar lines, clefs, time signatures and key signatures, may need
+to be printed twice when a line break occurs -- once at the end
+of the line and again at the start of the next line. Such
+objects are called @emph{breakable}, and have a property, the
+@code{break-visibility} property to control their visibility
+at the three positions in which they may appear -- at the
+start of a line, within a line if they are changed, and at the
+end of a line if a change takes place there.
+
+For example, the time signature
+by default will be printed at the start of the first line, but
+nowhere else unless it changes, when it will be printed at the
+point at which the change occurs. If this change occurs at the
+end of a line the new time signature will be printed at the start
+of the next line and a cautionary time signature will be printed
+at the end of the previous line as well.
+
+This behaviour is controlled by the @code{break-visibility}
+property, which is explained in
+@c Leave this ref on a newline - formats incorrectly otherwise -td
+@rlearning{Visibility and color of objects}. This property takes
+a vector of three booleans which, in order, determine whether the
+object is printed at the end of, within the body of, or at the
+beginning of a line. Or to be more precise, before a line break,
+where there is no line break, or after a line break.
+
+Alternatively, seven of the eight combinations may be specified
+by pre-defined functions, defined in @file{scm/output-lib.scm},
+where the last three columns indicate whether the layout objects
+will be visible in the positions shown at the head of the columns:
+
+@multitable @columnfractions .40 .15 .1 .1 .1
+@c TODO check these more carefully
+@headitem Function @tab Vector @tab Before @tab At no @tab After
+@headitem form @tab form @tab break @tab break @tab break
+
+@item @code{all-invisible} @tab @code{'#(#f #f #f)} @ @ @tab no @tab no @tab no
+@item @code{begin-of-line-visible} @tab @code{'#(#f #f #t)} @tab no @tab no @tab yes
+@item @code{end-of-line-visible} @tab @code{'#(#t #f #f)} @tab yes @tab no @tab no
+@item @code{all-visible} @tab @code{'#(#t #t #t)} @tab yes @tab yes @tab yes
+@c The center-visible function is not defined
+@c @item @code{center-visible} @tab @code{'#(#f #t #f)} @tab no @tab yes @tab no
+@item @code{begin-of-line-invisible} @tab @code{'#(#t #t #f)} @tab yes @tab yes @tab no
+@item @code{end-of-line-invisible} @tab @code{'#(#f #t #t)} @tab no @tab yes @tab yes
+@item @code{center-invisible} @tab @code{'#(#t #f #t)} @tab yes @tab no @tab yes
+@end multitable
+
+The @code{center-visible} function is not pre-defined.
+
+The default settings of @code{break-visibility} depend on the
+layout object. The following table shows all the layout objects
+of interest which are affected by @code{break-visibility} and the
+default setting of this property:
+
+@multitable @columnfractions .3 .3 .4
+
+@headitem Layout object @tab Usual context @tab Default setting
+
+@c omit Ambitus as it appears not to be affected by break-visibility -td
+@c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
+@item @code{BarLine} @tab @code{Score} @tab calculated
+@item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
+@c omit the following item until it can be explained -td
+@c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
+@item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
+@item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
+@item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
+@item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
+@c omit KeyCancellation until it can be explained -td
+@c @item @code{KeyCancellation} @tab ?? @tab @code{begin-of-line-invisible}
+@item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
+@c omit LeftEdge until it can be explained -td
+@c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
+@item @code{OctavateEight} @tab @code{Staff} @tab @code{begin-of-line-visible}
+@item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
+@item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
+
+@end multitable
+
+The example below shows the use of the vector form to control the
+visibility of barlines:
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+f4 g a b
+f4 g a b
+% Remove bar line at the end of the current line
+\once \override Score.BarLine #'break-visibility = #'#(#f #t #t)
+\break
+f4 g a b
+f4 g a b
+@end lilypond
+
+Although all three components of the vector used to override
+@code{break-visibility} must be present, not all of them are
+effective with every layout object, and some combinations may
+even give errors. The following limitations apply:
+
+@itemize @bullet
+@item Bar lines cannot be printed at start of line.
+@item A bar number cannot be printed at the start of the first
+line unless it is set to be different from 1.
+@item Clef -- see below
+@item Double percent repeats are either all printed or all
+suppressed. Use begin-of line-invisible to print and
+all-invisible to suppress.
+@item Key signature -- see below
+@item OctavateEight -- see below
@end itemize
+
+@node Special considerations
+@unnumberedsubsubsec Special considerations
+
+@strong{@emph{Visibility following explicit changes}}
+
+@cindex key signature, visibility following explicit change
+@cindex explicitKeySignatureVisibility
+@cindex clef, visibility following explicit change
+@cindex explicitClefVisibility
+
+The @code{break-visibility} property controls the visibility of
+key signatures and changes of clef only at the start of lines,
+i.e. after a break. It has no effect on the visibility of the
+key signature or clef following an explicit key change or an
+explicit clef change within or at the end of a line. In the
+following example the key signature following the explicit change
+to B-flat major is still visible, even though @code{all-invisible}
+is set.
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+\key g \major
+f4 g a b
+% Try to remove all key signatures
+\override Staff.KeySignature #'break-visibility = #all-invisible
+\key bes \major
+f4 g a b
+\break
+f4 g a b
+f4 g a b
+@end lilypond
+
+The visibility of such explicit key signature and clef changes is
+controlled by the @code{explicitKeySignatureVisibility} and
+@code{explicitClefVisibility} properties. These are the equivalent
+of the @code{break-visibility} property and both take a vector of
+three booleans or the predefined functions listed above, exactly like
+@code{break-visibility}. Both are properties of the Staff context,
+not the layout objects themselves, and so they are set using the
+@code{\set} command. Both are set by default to @code{all-visible}.
+These properties control only the visibility of key signatures and
+clefs resulting from explicit changes and do not affect key
+signatures and clefs at the beginning of lines;
+@code{break-visibility} must still be overridden in the appropriate
+object to remove these.
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+\key g \major
+f4 g a b
+\set Staff.explicitKeySignatureVisibility = #all-invisible
+\override Staff.KeySignature #'break-visibility = #all-invisible
+\key bes \major
+f4 g a b \break
+f4 g a b
+f4 g a b
+@end lilypond
+
+@strong{@emph{Visibility of cautionary accidentals}}
+
+To remove the cautionary accidentals printed at an explicit key
+change, set the Staff context property @code{printKeyCancellation}
+to @code{#f}:
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+\key g \major
+f4 g a b
+\set Staff.explicitKeySignatureVisibility = #all-invisible
+\set Staff.printKeyCancellation = ##f
+\override Staff.KeySignature #'break-visibility = #all-invisible
+\key bes \major
+f4 g a b \break
+f4 g a b
+f4 g a b
+@end lilypond
+
+With these overrides only the accidentals before the notes remain
+to indicate the change of key.
+
+@c TODO Add visibility of cautionary accidentals before notes
+
+@strong{@emph{Automatic bars}}
+
+@cindex automaticBars
+@cindex bar lines, suppressing
+
+As a special case, the printing of bar lines can also be turned off
+by setting the @code{automaticBars} property in the Score context.
+If set to @code{#f}, bar lines will not be printed automatically;
+they must be explicitly created with a @code{\bar} command. Unlike
+the @code{\cadenzaOn} predefined command, measures are still counted.
+Bar generation will resume according to that count if this property
+is later set to @code{#t}. When set to @code{#f}, line breaks can
+occur only at explicit @code{\bar} commands.
+
+@c TODO Add example
+
+@strong{@emph{Octavated clefs}}
+
+@cindex octavated clefs, visibility of
+@cindex visibility of octavated clefs
+@cindex clefs, visibility of octavation
+
+The small octavation symbol on octavated clefs is produced by the
+@code{OctavateEight} layout object. Its visibility is controlled
+independently from that of the @code{Clef} object, so it is
+necessary to apply any required @code{break-visibility} overrides
+to both the @code{Clef} and the @code{OctavateEight} layout objects
+to fully suppress such clef symbols at the start of each line.
+
+For explicit clef changes, the @code{explicitClefVisibility}
+property controls both the clef symbol and any octavation symbol
+associated with it.
+
+
+@seealso
+Learning Manual:
+@rlearning{Visibility and color of objects}
+
+
+@node Line styles
+@subsection Line styles
+
+@c TODO: split the following explanations between expressive marks and
+@c text-related stuff. Perhaps create a new subsection named
+@c "Spanner limits", "Spanner boundaries"? -vv
+
+Some performance indications, e.g., @i{rallentando} and
+@i{accelerando} and @i{trills} are written as text and are
+extended over many measures with lines, sometimes dotted or wavy.
+
+These all use the same routines as the glissando for drawing the
+texts and the lines, and tuning their behavior is therefore also
+done in the same way. It is done with a spanner, and the routine
+responsible for drawing the spanners is
+@code{ly:line-interface::print}. This routine determines the
+exact location of the two @i{span points} and draws a line in
+between, in the style requested.
+
+Here is an example of the different line styles available, and how
+to tune them.
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+d2 \glissando d'2
+\once \override Glissando #'style = #'dashed-line
+d,2 \glissando d'2
+\override Glissando #'style = #'dotted-line
+d,2 \glissando d'2
+\override Glissando #'style = #'zigzag
+d,2 \glissando d'2
+\override Glissando #'style = #'trill
+d,2 \glissando d'2
+@end lilypond
+
+The information that determines the end-points is computed
+on-the-fly for every graphic object, but it is possible to
+override these.
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+e2 \glissando f
+\once \override Glissando #'bound-details #'right #'Y = #-2
+e2 \glissando f
+@end lilypond
+
+The @code{Glissando} object, like any other using the
+@code{ly:line-interface::print} routine, carries a nested
+association list. In the above statement, the value for @code{Y}
+is set to @code{-2} for the association list corresponding to the
+right end point. Of course, it is also possible to adjust the
+left side with @code{left} instead of @code{right}.
+
+If @code{Y} is not set, the value is computed from the vertical
+position of right attachment point of the spanner.
+
+In case of a line break, the values for the span-points are
+extended with contents of the @code{left-broken} and
+@code{right-broken} sublists, for example
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+\override Glissando #'breakable = ##T
+\override Glissando #'bound-details #'right-broken #'Y = #-3
+c1 \glissando \break
+f1
+@end lilypond
+
+The following properties can be used for the
+
+@table @code
+@item Y
+This sets the Y-coordinate of the end point, in staff space. By
+default, it is the center of the bound object, so for a glissando
+it points to the vertical center of the note head.
+
+For horizontal spanners, such as text spanner and trill spanners,
+it is hardcoded to 0.
+
+@item attach-dir
+This determines where the line starts and ends in X-direction,
+relative to the bound object. So, a value of @code{-1} (or
+@code{LEFT}) makes the line start/end at the left side of the note
+head it is attached to.
+
+@item X
+This is the absolute coordinate of the end point. It is usually
+computed on the fly, and there is little use in overriding it.
+
+@item stencil
+Line spanners may have symbols at the beginning or end, which is
+contained in this sub-property. This is for internal use, it is
+recommended to use @code{text}.
+
+@item text
+This is a markup that is evaluated to yield stencil. It is used
+to put @i{cresc.} and @i{tr} on horizontal spanners.
+
+@lilypond[quote,ragged-right,fragment,relative=2,verbatim]
+\override TextSpanner #'bound-details #'left #'text
+ = \markup { \small \bold Slower }
+c2\startTextSpan b c a\stopTextSpan
+@end lilypond
+
+@item stencil-align-dir-y
+@item stencil-offset
+Without setting this, the stencil is simply put there at the
+end-point, as defined by the @code{X} and @code{Y} sub properties.
+Setting either @code{stencil-align-dir-y} or @code{stencil-offset}
+will move the symbol at the edge relative to the end point of the
+line
+
+@lilypond[relative=1,fragment,verbatim]
+\override TextSpanner #'bound-details
+ #'left #'stencil-align-dir-y = #DOWN
+\override TextSpanner #'bound-details
+ #'right #'stencil-align-dir-y = #UP
+
+\override TextSpanner #'bound-details
+ #'left #'text = #"gggg"
+\override TextSpanner #'bound-details
+ #'right #'text = #"hhhh"
+c4^\startTextSpan c c c \stopTextSpan
+@end lilypond
+
+@item arrow
+Setting this sub property to @code{#t} produce an arrowhead at the
+end of the line.
+
+@item padding
+This sub property controls the space between the specified
+end-point of the line and the actual end. Without padding, a
+glissando would start and end in the center of each note head.
+
+@end table
+
+@c TODO: Move to 5.4.4
+
+The music function \endSpanners terminates spanners and hairpins
+after exactly one note.
+
+@lilypond[verbatim,quote,ragged-right,relative=2,fragment]
+\endSpanners
+c2 \startTextSpan c2
+c2 \< c2
+@end lilypond
+
+When using \endSpanners it is not necessary to close
+\startTextSpan with \stopTextSpan, nor is it necessary to close
+hairpins with \!.
+
+
+
+@seealso
+
+Internals Reference: @rinternals{TextSpanner},
+@rinternals{Glissando}, @rinternals{VoiceFollower},
+@rinternals{TrillSpanner},
+@rinternals{line-spanner-interface}.
+
+
+@node Rotating objects
+@subsection Rotating objects
+
+Both layout objects and elements of markup text can be rotated by
+any angle about any point, but the method of doing so differs.
+
+@menu
+* Rotating layout objects::
+* Rotating markup::
+@end menu
+
+@node Rotating layout objects
+@unnumberedsubsubsec Rotating layout objects
+
+@cindex rotating objects
+@cindex objects, rotating
+
+All layout objects which support the @code{grob-interface} can be
+rotated by setting their @code{rotation} property. This takes a
+list of three items: the angle of rotation counter-clockwise,
+and the x and y coordinates of the point relative to the object's
+reference point about which the rotation is to be performed. The
+angle of rotation is specified in degrees and the coordinates in
+staff-spaces.
+
+The angle of rotation and the coordinates of the rotation point must
+be determined by trial and error.
+
+@cindex hairpins, angled
+@cindex angled hairpins
+
+There are only a few situations where the rotation of layout
+objects is useful; the following example shows one situation where
+they may be:
+
+@lilypond[quote,verbatim,relative=1]
+g4\< e' d' f\!
+\override Hairpin #'rotation = #'(20 -1 0)
+g,,4\< e' d' f\!
+@end lilypond
+
+@node Rotating markup
+@unnumberedsubsubsec Rotating markup
+
+All markup text can be rotated to lie at any angle by prefixing it
+with the @code{\rotate} command. The command takes two arguments:
+the angle of rotation in degrees counter-clockwise and the text to
+be rotated. The extents of the text are not rotated: they take
+their values from the extremes of the x and y coordinates of the
+rotated text. In the following example the
+@code{outside-staff-priority} property for text is set to @code{#f}
+to disable the automatic collision avoidance, which would push some
+of the text too high.
+
+@lilypond[quote,verbatim,relative=1]
+\override TextScript #'outside-staff-priority = ##f
+g4^\markup { \rotate #30 "a G" }
+b^\markup { \rotate #30 "a B" }
+des^\markup { \rotate #30 "a D-Flat" }
+fis^\markup { \rotate #30 "an F-Sharp" }
+@end lilypond
+
+
+@node Aligning objects
+@subsection Aligning objects
+
+@c FIXME Write this section
+
+
+@node Advanced tweaks
+@section Advanced tweaks
+
+@menu
+* Vertical grouping of grobs::
+* Modifying ends of spanners::
+* Modifying stencils::
+* Modifying shapes::
+@end menu
+
+
+
+
+@node Vertical grouping of grobs
+@subsection Vertical grouping of grobs
+
+@c FIXME Expand this section
+
+The VerticalAlignment and VerticalAxisGroup grobs work together.
+VerticalAxisGroup groups together different grobs like Staff, Lyrics,
+etc. VerticalAlignment then vertically aligns the different grobs
+grouped together by VerticalAxisGroup. There is usually only one
+VerticalAlignment per score but every Staff, Lyrics, etc. has its own
+VerticalAxisGroup.
+
+
+@node Modifying ends of spanners
+@subsection Modifying ends of spanners
+
+@c FIXME Write this section
+
+@node Modifying stencils
+@subsection Modifying stencils
+
+@c FIXME Write this section
+
+@node Modifying shapes
+@subsection Modifying shapes
+
+@c FIXME Write this section
+@c Discussion of Bezier curves and the control-points property
+
+@node Discussion of specific tweaks
+@section Discussion of specific tweaks
+
+@menu
+* old Contexts explained::
+@end menu
+
+
+@node old Contexts explained
+@subsection old Contexts explained
+
+@c FIXME Delete this section? It is in LM
+@c Or leave heading and go on from LM?
+
+When music is printed, a lot of notational elements must be added to the
+output. For example, compare the input and output of the following example:
+
+@lilypond[quote,verbatim,relative=2,fragment]
+cis4 cis2. g4
+@end lilypond
+
+The input is rather sparse, but in the output, bar lines, accidentals,
+clef, and time signature are added. LilyPond @emph{interprets} the
+input. During this step, the musical information is inspected in time
+order, similar to reading a score from left to right. While reading
+the input, the program remembers where measure boundaries are, and which
+pitches require explicit accidentals. This information can be presented on
+several levels. For example, the effect of an accidental is limited
+to a single staff, while a bar line must be synchronized across the
+entire score.
+
+Within LilyPond, these rules and bits of information are grouped in
+@emph{Contexts}. Some examples of contexts are @code{Voice},
+@code{Staff}, and @code{Score}. They are hierarchical, for
+example: a @code{Staff} can contain many @code{Voice}s, and a
+@code{Score} can contain many @code{Staff} contexts.
+
+@quotation
+@sourceimage{context-example,5cm,,}
+@end quotation
+
+Each context has the responsibility for enforcing some notation rules,
+creating some notation objects and maintaining the associated
+properties. For example, the @code{Voice} context may introduce an
+accidental and then the @code{Staff} context maintains the rule to
+show or suppress the accidental for the remainder of the measure. The
+synchronization of bar lines is handled at @code{Score} context.
+
+However, in some music we may not want the bar lines to be
+synchronized -- consider a polymetric score in 4/4 and 3/4 time. In
+such cases, we must modify the default settings of the @code{Score}
+and @code{Staff} contexts.
+
+For very simple scores, contexts are created implicitly, and you need
+not be aware of them. For larger pieces, such as anything with more
+than one staff, they must be
+created explicitly to make sure that you get as many staves as you
+need, and that they are in the correct order. For typesetting pieces
+with specialized notation, it can be useful to modify existing or
+to define new contexts.
+
+
+A complete description of all available contexts is in the program
+reference, see
+@ifhtml
+@rinternals{Contexts}.
+@end ifhtml
+@ifnothtml
+Translation @expansion{} Context.
+@end ifnothtml
+
+@c [TODO: describe propagation]
+
+
+
projects / lilypond.git / blobdiff