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@c -*- coding: utf-8; mode: texinfo; -*-
@c This file is part of lilypond-learning.tely
@ignore
    Translation of GIT committish: FILL-IN-HEAD-COMMITTISH

    When revising a translation, copy the HEAD committish of the
    version that you are working on.  See TRANSLATION for details.
@end ignore

@node Introduction
@chapter Introduction


@menu
* Engraving::                   
* Automated engraving::         
* What symbols to engrave?::    
* Music representation::        
* Example applications::        
* About this manual::           
@end menu


@node Engraving
@section Engraving

The art of music typography is called @emph{(plate) engraving}.  The
term derives from the traditional process of music printing.  Just a
few decades ago, sheet music was made by cutting and stamping the
music into a zinc or pewter plate in mirror image.  The plate would be
inked, the depressions caused by the cutting and stamping would hold
ink.  An image was formed by pressing paper to the plate.  The
stamping and cutting was completely done by hand.  Making a correction
was cumbersome, if possible at all, so the engraving had to be perfect
in one go.  Engraving was a highly specialized skill; a craftsman had
to complete around five years of training before earning the title of
master engraver, and another five years of experience were
necessary to become truly skilled.

Nowadays, all newly printed music is produced with computers.  This
has obvious advantages; prints are cheaper to make, and editorial work
can be delivered by email.  Unfortunately, the pervasive use of
computers has also decreased the graphical quality of scores.
Computer printouts have a bland, mechanical look, which makes them
unpleasant to play from.


@c introduce illustrating aspects of engraving, font...
The images below illustrate the difference between traditional
engraving and typical computer output, and the third picture shows how
LilyPond mimics the traditional look.  The left picture shows a scan
of a flat symbol from an edition published in 2000.  The center
depicts a symbol from a hand-engraved Bärenreiter edition of the
same music.  The left scan illustrates typical flaws of computer
print: the staff lines are thin, the weight of the flat symbol matches
the light lines and it has a straight layout with sharp corners.  By
contrast, the Bärenreiter flat has a bold, almost voluptuous
rounded look.  Our flat symbol is designed after, among others, this
one.  It is rounded, and its weight harmonizes with the thickness of
our staff lines, which are also much thicker than lines in the
computer edition.

@multitable @columnfractions .125 .25 .25 .25 .125
@item @tab
@ifnotinfo
@iftex
@image{henle-flat-gray,,4cm}
@end iftex
@ifnottex
@image{henle-flat-gray,,,png}
@end ifnottex

@tab
@iftex
@image{baer-flat-gray,,4cm}
@end iftex
@ifnottex
@image{baer-flat-gray,,,png}
@end ifnottex

@tab
@iftex
@image{lily-flat-bw,,4cm}
@end iftex
@ifnottex
@image{lily-flat-bw,,,png}
@end ifnottex
@end ifnotinfo
@ifinfo
@image{lilypond/henle-flat-bw,,,png} @image{lilypond/baer-flat-bw,,,png}
@image{lilypond/lily-flat-bw,,,png}
@end ifinfo

@item @tab
Henle (2000)
@tab
Bärenreiter (1950)
@tab
LilyPond Feta font (2003)

@end multitable


@cindex musical symbols
@cindex font
@cindex blackness
@cindex balance

@c introduce illustrating aspects of engraving, spacing...
In spacing, the distribution of space should reflect the durations
between notes.  However, many modern scores adhere to the durations
with mathematical precision, which leads to poor results.  In the next
example a motive is printed twice: once using exact mathematical
spacing, and once with corrections.  Can you spot which fragment is
which?

@cindex optical spacing
@c file spacing-optical.
@c need to include it here,  because we want two images.
@lilypond
\paper {
  ragged-right = ##t
  indent = #0.0
}

music = {
   c'4 e''4 e'4 b'4 |
   \stemDown
   b'8[ e'' a' e'']
   \stemNeutral
   e'8[ e'8 e'8 e'8]
}

\score
{
  \music
  \layout {
    \context {
      \Staff
      \override NoteSpacing #'stem-spacing-correction = #0.6
    }
  }
}
@end lilypond

@lilypond
\paper {
  ragged-right = ##t
  indent = #0.0
}

music = {
   c'4 e''4 e'4 b'4 |
   \stemDown
   b'8[ e'' a' e'']
   \stemNeutral
   e'8[ e'8 e'8 e'8]
}
\score
{
  \music
  \layout {
    \context {
      \Staff
      \override NoteSpacing #'stem-spacing-correction = #0.0
      \override NoteSpacing #'same-direction-correction = #0.0
      \override StaffSpacing #'stem-spacing-correction = #0.0
    }
  }
}
@end lilypond

@cindex regular rhythms
@cindex regular spacing

Each bar in the fragment only uses notes that are played in a constant
rhythm.  The spacing should reflect that.  Unfortunately, the eye
deceives us a little; not only does it notice the distance between
note heads, it also takes into account the distance between
consecutive stems.  As a result, the notes of an up-stem/@/down-stem
combination should be put farther apart, and the notes of a
down-stem/@/up-stem combination should be put closer together, all
depending on the combined vertical positions of the notes.  The upper
two measures are printed with this correction, the lower two measures
without, forming down-stem/@/up-stem clumps of notes.

@cindex typography

Musicians are usually more absorbed with performing than with studying
the looks of a piece of music, so nitpicking about typographical
details may seem academical.  But it is not.  In larger pieces with
monotonous rhythms, spacing corrections lead to subtle variations in
the layout of every line, giving each one a distinct visual signature.
Without this signature all lines would look the same, and they become
like a labyrinth.  If a musician looks away once or has a lapse in
concentration, the lines might lose their place on the page.

Similarly, the strong visual look of bold symbols on heavy staff lines
stands out better when the music is far away from the reader, for
example, if it is on a music stand.  A careful distribution of white
space allows music to be set very tightly without cluttering symbols
together.  The result minimizes the number of page turns, which is a
great advantage.

This is a common characteristic of typography.  Layout should be
pretty, not only for its own sake, but especially because it helps the
reader in her task.  For performance material like sheet music, this
is of double importance: musicians have a limited amount of attention.
The less attention they need for reading, the more they can focus on
playing the music.  In other words, better typography translates to
better performances.

These examples demonstrate that music typography is an art that is
subtle and complex, and that producing it requires considerable
expertise, which musicians usually do not have.  LilyPond is our
effort to bring the graphical excellence of hand-engraved music to the
computer age, and make it available to normal musicians.  We have
tuned our algorithms, font-designs, and program settings to produce
prints that match the quality of the old editions we love to see and
love to play from.




@node Automated engraving
@section Automated engraving

How do we go about implementing typography?  If craftsmen need over
ten years to become true masters, how could we simple hackers ever
write a program to take over their jobs?

The answer is: we cannot.  Typography relies on human judgment of
appearance, so people cannot be replaced completely.  However, much of
the dull work can be automated.  If LilyPond solves most of the common
situations correctly, this will be a huge improvement over existing
software.  The remaining cases can be tuned by hand.  Over the course
of years, the software can be refined to do more and more things
automatically, so manual overrides are less and less necessary.

When we started, we wrote the LilyPond program entirely in the C++
programming language; the program's functionality was set in stone by
the developers.  That proved to be unsatisfactory for a number of
reasons:

@itemize
@item When LilyPond makes mistakes,
users need to override formatting decisions.  Therefore, the user must
have access to the formatting engine.  Hence, rules and settings cannot
be fixed by us at compile-time but must be accessible for users at
run-time.

@item Engraving is a matter of visual judgment, and therefore a matter of
taste.  As knowledgeable as we are, users can disagree with our
personal decisions.  Therefore, the definitions of typographical style
must also be accessible to the user.

@item Finally, we continually refine the formatting algorithms, so we
need a flexible approach to rules.  The C++ language forces a certain
method of grouping rules that do not match well with how music
notation works.
@end itemize

These problems have been addressed by integrating an interpreter for
the Scheme programming language and rewriting parts of LilyPond in
Scheme.  The current formatting architecture is built around the
notion of graphical objects, described by Scheme variables and
functions.  This architecture encompasses formatting rules,
typographical style and individual formatting decisions.  The user has
direct access to most of these controls.

Scheme variables control layout decisions.  For example, many
graphical objects have a direction variable that encodes the choice
between up and down (or left and right).  Here you see two chords,
with accents and arpeggios.  In the first chord, the graphical objects
have all directions down (or left).  The second chord has all
directions up (right).

@lilypond[quote,ragged-right]
\new Score \with {
   \override SpacingSpanner #'spacing-increment = #3
   \override TimeSignature #'transparent = ##t
} \relative {
   \stemDown <e g b>4_>-\arpeggio
   \override Arpeggio #'direction = #RIGHT
   \stemUp <e g b>4^>-\arpeggio
}
@end lilypond

@noindent
The process of formatting a score consists of reading and writing the
variables of graphical objects.  Some variables have a preset value.  For
example, the thickness of many lines -- a characteristic of typographical
style -- is a variable with a preset value.  You are free to alter this
value, giving your score a different typographical impression.

@lilypond[quote,ragged-right]
fragment = {
   \clef bass f8 as8
   c'4-~ c'16 as g f e16 g bes c' des'4
}
<<
   \new Staff \fragment
   \new Staff \with {
      \override Beam #'thickness = #0.3
      \override Stem #'thickness = #0.5
      \override Bar #'thickness = #3.6
      \override Tie #'thickness = #2.2
      \override StaffSymbol #'thickness = #3.0
      \override Tie #'extra-offset = #'(0 .  0.3)
      }
      \fragment
>>
@end lilypond

Formatting rules are also preset variables: each object has variables
containing procedures.  These procedures perform the actual
formatting, and by substituting different ones, we can change the
appearance of objects.  In the following example, the rule which note
head objects are used to produce their symbol is changed during the
music fragment.

@lilypond[quote,ragged-right]
#(set-global-staff-size 30)

#(define (mc-squared grob orig current)
  (let* ((interfaces (ly:grob-interfaces grob))
         (pos (ly:grob-property grob 'staff-position)))
    (if (memq 'note-head-interface interfaces)
        (begin
          (ly:grob-set-property! grob 'stencil ly:text-interface::print)
          (ly:grob-set-property! grob 'font-family 'roman)
          (ly:grob-set-property! grob 'text
            (make-raise-markup -0.5
              (case pos
                ((-5) (make-simple-markup "m"))
                ((-3) (make-simple-markup "c "))
                ((-2) (make-smaller-markup (make-bold-markup "2")))
                (else (make-simple-markup "bla")))))))))

\new Voice \relative c' {
   \stemUp
   \set autoBeaming = ##f
   \time 2/4
   <d f g>4
   \once \override NoteHead #'stencil = #ly:note-head::brew-ez-stencil
   \once \override NoteHead #'font-size = #-7
   \once \override NoteHead #'font-family = #'sans
   \once \override NoteHead #'font-series = #'bold
   <d f g>
   \once \override NoteHead #'style = #'cross
   <d f g>
   \applyOutput #'Voice #mc-squared
   <d f g>
   <<
      { d8[ es-( fis^^ g] fis2-) }
      \repeat unfold 5 { \applyOutput #'Voice #mc-squared s8 }
   >>
}
@end lilypond



@node What symbols to engrave?
@section What symbols to engrave?

@cindex engraving
@cindex typography

The formatting process decides where to place symbols.  However, this
can only be done once it is decided @emph{what} symbols should be
printed, in other words what notation to use.

Common music notation is a system of recording music that has evolved
over the past 1000 years.  The form that is now in common use dates
from the early renaissance.  Although the basic form (i.e., note heads
on a 5-line staff) has not changed, the details still evolve to
express the innovations of contemporary notation.  Hence, it
encompasses some 500 years of music.  Its applications range from
monophonic melodies to monstrous counterpoints for large orchestras.

How can we get a grip on such a many-headed beast, and force it into
the confines of a computer program?  Our solution is to break up the
problem of notation (as opposed to engraving, i.e., typography) into
digestible and programmable chunks: every type of symbol is handled by
a separate module, a so-called plug-in.  Each plug-in is completely
modular and independent, so each can be developed and improved
separately.  Such plug-ins are called @code{engraver}s, by analogy
with craftsmen who translate musical ideas to graphic symbols.

In the following example, we see how we start out with a plug-in for
note heads, the @code{Note_heads_engraver}.

@lilypond[quote,ragged-right]
\include "engraver-example.ily"

\score {
   \topVoice
   \layout {
   \context {
      \Voice
      \remove "Stem_engraver"
      \remove "Phrasing_slur_engraver"
      \remove "Slur_engraver"
      \remove "Script_engraver"
      \remove "Beam_engraver"
      \remove "Auto_beam_engraver"
   }
   \context {
      \Staff
      \remove "Accidental_engraver"
      \remove "Key_engraver"
      \remove "Clef_engraver"
      \remove "Bar_engraver"
      \remove "Time_signature_engraver"
      \remove "Staff_symbol_engraver"
      \consists "Pitch_squash_engraver"
   }
}
}
@end lilypond

@noindent
Then a @code{Staff_symbol_engraver} adds the staff

@lilypond[quote,ragged-right]
\include "engraver-example.ily"

\score {
  \topVoice
  \layout {
    \context {
      \Voice
      \remove "Stem_engraver"
      \remove "Phrasing_slur_engraver"
      \remove "Slur_engraver"
      \remove "Script_engraver"
      \remove "Beam_engraver"
      \remove "Auto_beam_engraver"
    }
    \context {
      \Staff
      \remove "Accidental_engraver"
      \remove "Key_engraver"
      \remove "Clef_engraver"
      \remove "Bar_engraver"
      \consists "Pitch_squash_engraver"
      \remove "Time_signature_engraver"
    }
  }
}
@end lilypond

@noindent
the @code{Clef_engraver} defines a reference point for the staff

@lilypond[quote,ragged-right]
\include "engraver-example.ily"

\score {
  \topVoice
  \layout {
    \context {
      \Voice
      \remove "Stem_engraver"
      \remove "Phrasing_slur_engraver"
      \remove "Slur_engraver"
      \remove "Script_engraver"
      \remove "Beam_engraver"
      \remove "Auto_beam_engraver"
    }
    \context {
      \Staff
      \remove "Accidental_engraver"
      \remove "Key_engraver"
      \remove "Bar_engraver"
      \remove "Time_signature_engraver"
    }
  }
}
@end lilypond

@noindent
and the @code{Stem_engraver} adds stems.

@lilypond[quote,ragged-right]
\include "engraver-example.ily"

\score {
  \topVoice
  \layout {
    \context {
      \Voice
      \remove "Phrasing_slur_engraver"
      \remove "Slur_engraver"
      \remove "Script_engraver"
      \remove "Beam_engraver"
      \remove "Auto_beam_engraver"
    }
    \context {
      \Staff
      \remove "Accidental_engraver"
      \remove "Key_engraver"
      \remove "Bar_engraver"
      \remove "Time_signature_engraver"
    }
  }
}
@end lilypond

@noindent
The @code{Stem_engraver} is notified of any note head coming along.
Every time one (or more, for a chord) note head is seen, a stem
object is created and connected to the note head.  By adding
engravers for beams, slurs, accents, accidentals, bar lines,
time signature, and key signature, we get a complete piece of
notation.

@lilypond[quote,ragged-right]
\include "engraver-example.ily"
\score { \topVoice }
@end lilypond

This system works well for monophonic music, but what about
polyphony?  In polyphonic notation, many voices can share a staff.

@lilypond[quote,ragged-right]
\include "engraver-example.ily"
\new Staff << \topVoice \\ \botVoice >>
@end lilypond

In this situation, the accidentals and staff are shared, but the stems,
slurs, beams, etc., are private to each voice.  Hence, engravers should
be grouped.  The engravers for note heads, stems, slurs, etc., go into a
group called @q{Voice context,} while the engravers for key, accidental,
bar, etc., go into a group called @q{Staff context.}  In the case of
polyphony, a single Staff context contains more than one Voice context.
Similarly, multiple Staff contexts can be put into a single Score
context.  The Score context is the top level notation context.

@seealso

Internals Reference: @internalsref{Contexts}.

@lilypond[quote,ragged-right]
\include "engraver-example.ily"
\score {
   <<
      \new Staff << \topVoice \\ \botVoice >>
      \new Staff << \pah \\ \hoom >>
   >>
}
@end lilypond

@node Music representation
@section Music representation

Ideally, the input format for any high-level formatting system is an
abstract description of the content.  In this case, that would be the
music itself.  This poses a formidable problem: how can we define what
music really is? Instead of trying to find an answer, we have reversed
the question.  We write a program capable of producing sheet music,
and adjust the format to be as lean as possible.  When the format can
no longer be trimmed down, by definition we are left with content
itself.  Our program serves as a formal definition of a music
document.

The syntax is also the user-interface for LilyPond, hence it is easy
to type

@example
@{
  c'4 d'8
@}
@end example

@noindent
a quarter note C1 (middle C) and an eighth note D1 (D above middle C)

@lilypond[quote]
{
  c'4 d'8
}
@end lilypond

On a microscopic scale, such syntax is easy to use.  On a larger
scale, syntax also needs structure.  How else can you enter complex
pieces like symphonies and operas?  The structure is formed by the
concept of music expressions: by combining small fragments of music
into larger ones, more complex music can be expressed.  For example

@lilypond[quote,verbatim,fragment,relative=1]
c4
@end lilypond

@noindent
Chords can be constructed with @code{<<} and @code{>>} enclosing the notes

@c < > is not a music expression,
@c so we use <<>> iso. <> to drive home the point of
@c expressions.  Don't change this back --hwn.
@example
<<c4 d4 e4>>
@end example

@lilypond[quote,fragment,relative=1]
\new Voice { <<c4 d4 e>> }
@end lilypond

@noindent
This expression is put in sequence by enclosing it in curly braces
@code{@{@tie{}@dots{}@tie{}@}}

@example
@{ f4 <<c4 d4 e4>> @}
@end example

@lilypond[quote,relative=1,fragment]
{ f4 <<c d e4>> }
@end lilypond

@noindent
The above is also an expression, and so it may be combined
again with another simultaneous expression (a half note) using <<,
@code{\\}, and >>

@example
<< g2 \\ @{ f4 <<c4 d4 e4>> @} >>
@end example

@lilypond[quote,fragment,relative=2]
\new Voice { << g2 \\ { f4 <<c d e>> } >> }
@end lilypond

Such recursive structures can be specified neatly and formally in a
context-free grammar.  The parsing code is also generated from this
grammar.  In other words, the syntax of LilyPond is clearly and
unambiguously defined.

User-interfaces and syntax are what people see and deal with
most.  They are partly a matter of taste, and also subject of much
discussion.  Although discussions on taste do have their merit, they
are not very productive.  In the larger picture of LilyPond, the
importance of input syntax is small: inventing neat syntax is easy, while
writing decent formatting code is much harder.  This is also
illustrated by the line-counts for the respective components: parsing
and representation take up less than 10% of the source code.


@node Example applications
@section Example applications

We have written LilyPond as an experiment of how to condense the art
of music engraving into a computer program.  Thanks to all that hard
work, the program can now be used to perform useful tasks.  The
simplest application is printing notes.

@lilypond[quote,relative=1]
{
  \time 2/4
  c4 c g'4 g a4 a g2
}
@end lilypond

@noindent
By adding chord names and lyrics we obtain a lead sheet.

@lilypond[quote,ragged-right]
<<
   \chords { c2 c f2 c }
   \new Staff \relative c' { \time 2/4 c4 c g'4 g a4 a g2 }
   \new Lyrics \lyricmode { twin4 kle twin kle lit tle star2 }
>>
@end lilypond

Polyphonic notation and piano music can also be printed.  The following
example combines some more exotic constructs.

@lilypondfile[quote,ragged-right]{screech-boink.ly}

The fragments shown above have all been written by hand, but that is
not a requirement.  Since the formatting engine is mostly automatic, it
can serve as an output means for other programs that manipulate
music.  For example, it can also be used to convert databases of
musical fragments to images for use on websites and multimedia
presentations.

This manual also shows an application: the input format is text, and
can therefore be easily embedded in other text-based formats such as
@LaTeX{}, HTML, or in the case of this manual, Texinfo.  By means of a
special program, the input fragments can be replaced by music images
in the resulting PDF or HTML output files.  This makes it easy
to mix music and text in documents.



@node About this manual
@section About this manual

FIXME: needs almost-complete rewrite.  -gp

There are four manuals about LilyPond: the @emph{Learning Manual},
the @emph{Notation Reference}, the @emph{Application Usage}, and the
@emph{Internals Reference}.


@subheading Learning Manual (LM)

This book explains how to begin learning LilyPond, as well as explaining
some key concepts in easy terms.  It is recommended to read these
chapters in a linear fashion.

@itemize

@item
@ifhtml
The
@end ifhtml
@emph{@ref{Tutorial}},
gives a gentle introduction to typesetting music.  First time
users should start here.

@item
@emph{@ref{Fundamental concepts}},
explains some general concepts about the lilypond file format.  If
you are not certain where to place a command, read this chapter!

@item
@emph{@ref{Working on LilyPond projects}},
discusses practical uses of LilyPond and how to avoid some common
problems.

@item
@emph{@ref{Tweaking output}},
shows how to change the default engraving that LilyPond
produces.

@end itemize


@subheading Notation Reference (NR)

This book explains all the LilyPond commands which produce notation.  It
assumes that readers are familiar with the concepts in the Learning
manual.

All of this needs to be rewritten after GDP, anyway.

@ignore

@itemize

@item
@emph{@r ef{Basic notation}},
discusses topics grouped by notation construct.  This section gives
details about basic notation that will be useful in almost any
notation project.

@item
@emph{@r ef{Instrument-specific notation}},
discusses topics grouped by notation construct.  This section gives
details about special notation that will only be useful for particular
instrument (or vocal) groups.

@item
@emph{@r ef{Advanced notation}},
discusses topics grouped by notation construct.  This section gives
details about complicated or unusual notation.

@item
@emph{@r ef{Changing defaults}},
explains how to fine tune layout.

@item
@emph{@r ef{Non-musical notation}},
discusses non-musical output such as titles, multiple movements,
and how to select which MIDI instruments to use.

@item
@emph{@r ef{Spacing issues}},
discusses issues which affect the global output, such as selecting
paper size or specifying page breaks.

@item
@emph{@r ef{Interfaces for programmers}},
explains how to create music functions.

@end itemize


@subsubheading Appendices

This book contains useful reference charts.

@itemize
@item
@ifhtml
The
@end ifhtml
@emph{@r ef{Literature list}},
contains a set of useful reference books for those who wish to know
more on notation and engraving.

@item
The
@emph{@r ef{Scheme tutorial}},
presents a short introduction to Scheme, the programming
language that music functions use.

@item
@emph{@r ef{Notation manual tables}},
are a set of tables showing the chord names, MIDI instruments,
a list of color names, and the Feta font.

@item
@emph{@r ef{Templates}},
of LilyPond pieces.  Just cut and paste a
template into a file, add notes, and you're done!

@item
The
@emph{@r ef{Cheat sheet}},
is a handy reference of the most common LilyPond commands.

@item
The
@emph{@r ef{LilyPond command index}},
is an index of all LilyPond @code{\commands}.

@item
The
@emph{@r ef{LilyPond index}},
is a complete index.

@end itemize

@end ignore

@subheading Program usage

This book explains how to execute the program and how to integrate
LilyPond notation with other programs.

@itemize

@item
@emph{@rprogram{Install}},
explains how to install LilyPond (including compilation if desired).

@item
@emph{@rprogram{Setup}},
describes how to configure your computer for optimum LilyPond usage,
such as using special environments for certain text editors.

@item
@emph{@rprogram{Running LilyPond}},
shows how to run LilyPond and its helper programs.  In addition, this
section explains how to upgrade input files from previous versions of
LilyPond.

@item
@emph{@rprogram{LilyPond-book}},
explains the details behind creating
documents with in-line music examples, like this manual.

@item
@emph{@rprogram{Converting from other formats}},
explains how to run the conversion programs.  These programs are
supplied with the LilyPond package, and convert a variety of music
formats to the @code{.ly} format.

@end itemize



@subsubheading Other information

There are a number of other places which may be very valuable.

@itemize
@cindex idiom
@cindex jargon
@cindex terminology
@cindex foreign languages
@cindex language
@item
@ifnottex
The @ref{Top,Music glossary,,music-glossary}, explains musical terms and
includes translations to various languages.  It is also available in
PDF.
@end ifnottex
@iftex
The music glossary explains musical terms, and includes translations
to various languages.  It is a separate document, available in HTML
and PDF.
@end iftex
If you are not familiar with music notation or music terminology
(especially if you are a non-native English speaker), it is highly
advisable to consult the glossary.

@cindex snippets
@cindex LSR
@item
The
@ifhtml
@uref{source/input/lsr/snippets/index.html,Snippets}
@end ifhtml
@ifnothtml
Snippets
@end ifnothtml
are a great collection of short examples which demonstrate tricks, tips,
and special features of LilyPond.  Most of these snippets can also be
found in the @uref{http://lsr.dsi.unimi.it/,LilyPond Snippet
Repository}.  This website also has a searchable LilyPond manual.


@item
The
@iftex
Internals Reference
@end iftex
@ifnottex
@ref{Top,Internals Reference,,lilypond-internals}
@end ifnottex
is a set of heavily cross linked HTML pages, which document the
nitty-gritty details of each and every LilyPond class, object, and
function.  It is produced directly from the formatting definitions used.

Almost all formatting functionality that is used internally, is
available directly to the user.  For example, all variables that control
thickness values, distances, etc., can be changed in input files.  There
are a huge number of formatting options, and all of them are described
in this document.  Each section of the notation manual has a @b{See
also} subsection, which refers to the generated documentation.  In the
HTML document, these subsections have clickable links.

@end itemize


Once you are an experienced user, you can use the manual as reference:
there is an extensive index@footnote{If you are looking for something,
and you cannot find it in the manual, that is considered a bug.  In
that case, please file a bug report.}, but the document is also
available in
@iftex
a big HTML page,
@end iftex
@ifhtml
@uref{source/Documentation/user/lilypond-big-page.html, one big page},
@end ifhtml
which can be searched easily using the search facility of a web
browser.


In all HTML documents that have music fragments embedded, the LilyPond
input that was used to produce that image can be viewed by clicking
the image.

The location of the documentation files that are mentioned here can vary
from system to system.  On occasion, this manual refers to
initialization and example files.  Throughout this manual, we refer to
input files relative to the top-directory of the source archive.  For
example, @file{input/@/lsr/@/dirname/@/bla@/.ly} may refer to the file
@file{lilypond@/2.x.y/@/input/@/lsr/@/dirname/@/bla@/.ly}.  On binary
packages for the Unix platform, the documentation and examples can
typically be found somewhere below
@file{/usr/@/share/@/doc/@/lilypond/}.  Initialization files, for
example @file{scm/@/lily@/.scm}, or @file{ly/@/engraver@/-init@/.ly},
are usually found in the directory @file{/usr/@/share/@/lilypond/}.

@cindex adjusting output
@cindex variables
@cindex properties
@cindex lilypond-internals
@cindex internal documentation
@cindex Scheme
@cindex extending lilypond
@cindex index

Finally, this and all other manuals, are available online both as PDF
files and HTML from the web site, which can be found at
@uref{http://@/www@/.lilypond@/.org/}.