Merge branch 'lilypond/translation' of ssh://git.sv.gnu.org/srv/git/lilypond into...

[lilypond.git] / Documentation / notation / input.itely

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

@ignore
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@c \version "2.12.0"

@node General input and output
@chapter General input and output

This section deals with general LilyPond input and output issues,
rather than specific notation.

@menu
* Input structure::
* Titles and headers::
* Working with input files::
* Controlling output::
* MIDI output::
@end menu


@node Input structure
@section Input structure

The main format of input for LilyPond are text files.  By convention,
these files end with @code{.ly}.

@menu
* Structure of a score::
* Multiple scores in a book::
* File structure::
@end menu


@node Structure of a score
@subsection Structure of a score

@funindex \score

A @code{\score} block must contain a single music expression
delimited by curly brackets:

@example
\score @{
...
@}
@end example

@warning{There must be @strong{only one} outer music expression in
a @code{\score} block, and it @strong{must} be surrounded by
curly brackets.}

This single music expression may be of any size, and may contain
other music expressions to any complexity.  All of these examples
are music expressions:

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

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

@lilypond[verbatim,quote]
<<
  \new Staff { c'4 c' c' c' }
  \new Staff { d'4 d' d' d' }
>>
@end lilypond

@example
@{
  \new GrandStaff <<
    \new StaffGroup <<
      \new Staff @{ \flute @}
      \new Staff @{ \oboe @}
    >>
    \new StaffGroup <<
      \new Staff @{ \violinI @}
      \new Staff @{ \violinII @}
    >>
  >>
@}
@end example

Comments are one exception to this general rule.  (For others see
@ref{File structure}.)  Both single-line comments and comments
delimited by @code{%@{ .. %@}} may be placed anywhere within an
input file.  They may be placed inside or outside a @code{\score}
block, and inside or outside the single music expression within a
@code{\score} block.


@seealso
Learning Manual:
@rlearning{Working on input files},
@rlearning{Music expressions explained},
@rlearning{Score is a (single) compound musical expression}.


@node Multiple scores in a book
@subsection Multiple scores in a book

@funindex \book
@cindex movements, multiple

A document may contain multiple pieces of music and text.  Examples
of these are an etude book, or an orchestral part with multiple
movements.  Each movement is entered with a @code{\score} block,

@example
\score @{
  @var{..music..}
@}
@end example

and texts are entered with a @code{\markup} block,

@example
\markup @{
  @var{..text..}
@}
@end example

@funindex \book

All the movements and texts which appear in the same @code{.ly} file
will normally be typeset in the form of a single output file.

@example
\score @{
  @var{..}
@}
\markup @{
  @var{..}
@}
\score @{
  @var{..}
@}
@end example

However, if you want multiple output files from the same @code{.ly}
file, then you can add multiple @code{\book} blocks, where each such
@code{\book} block will result in a separate output.  If you do not
specify any @code{\book} block in the file, LilyPond will implicitly
treat the full file as a single @code{\book} block, see @ref{File
structure}.  One important exception is within lilypond-book documents,
where you explicitly have to add a @code{\book} block, otherwise only
the first @code{\score} or @code{\markup} will appear in the output.

The header for each piece of music can be put inside the @code{\score}
block.  The @code{piece} name from the header will be printed before
each movement.  The title for the entire book can be put inside the
@code{\book}, but if it is not present, the @code{\header} which is at
the top of the file is inserted.

@example
\header @{
  title = "Eight miniatures"
  composer = "Igor Stravinsky"
@}
\score @{
  @dots{}
  \header @{ piece = "Romanze" @}
@}
\markup @{
   ..text of second verse..
@}
\markup @{
   ..text of third verse..
@}
\score @{
  @dots{}
  \header @{ piece = "Menuetto" @}
@}
@end example

@funindex \bookpart

Pieces of music may be grouped into book parts using @code{\bookpart}
blocks.  Book parts are separated by a page break, and can start with a
title, like the book itself, by specifying a @code{\header} block.

@example
\bookpart @{
  \header @{
    title = "Book title"
    subtitle = "First part"
  @}
  \score @{ @dots{} @}
  @dots{}
@}
\bookpart @{
  \header @{
    subtitle = "Second part"
  @}
  \score @{ @dots{} @}
  @dots{}
@}
@end example

@node File structure
@subsection File structure

@funindex \paper
@funindex \midi
@funindex \layout
@funindex \header
@funindex \score
@funindex \book
@funindex \bookpart

A @code{.ly} file may contain any number of toplevel expressions, where a
toplevel expression is one of the following:

@itemize @bullet
@item
An output definition, such as @code{\paper}, @code{\midi}, and
@code{\layout}.  Such a definition at the toplevel changes the default
book-wide settings.  If more than one such definition of
the same type is entered at the top level any definitions in the later
expressions have precedence.

@item
A direct scheme expression, such as
@code{#(set-default-paper-size "a7" 'landscape)} or
@code{#(ly:set-option 'point-and-click #f)}.

@item
A @code{\header} block.  This sets the global header block.  This
is the block containing the definitions for book-wide settings, like
composer, title, etc.

@item
A @code{\score} block.  This score will be collected with other
toplevel scores, and combined as a single @code{\book}.
This behavior can be changed by setting the variable
@code{toplevel-score-handler} at toplevel.  The default handler is
defined in the init file @file{../@/scm/@/lily@/.scm}.

@item
A @code{\book} block logically combines multiple movements
(i.e., multiple @code{\score} blocks) in one document.  If there
are a number of @code{\score}s, one output file will be created
for each @code{\book} block, in which all corresponding movements
are concatenated.  The only reason to explicitly specify
@code{\book} blocks in a @code{.ly} file is if you wish to create
multiple output files from a single input file.  One exception is
within lilypond-book documents, where you explicitly have to add
a @code{\book} block if you want more than a single @code{\score}
or @code{\markup} in the same example.  This behavior can be
changed by setting the variable @code{toplevel-book-handler} at
toplevel.  The default handler is defined in the init file
@file{../@/scm/@/lily@/.scm}.

@item
A @code{\bookpart} block.  A book may be divided into several parts,
using @code{\bookpart} blocks, in order to ease the page breaking,
or to use different @code{\paper} settings in different parts.

@item
A compound music expression, such as
@example
@{ c'4 d' e'2 @}
@end example

This will add the piece in a @code{\score} and format it in a
single book together with all other toplevel @code{\score}s and music
expressions.  In other words, a file containing only the above
music expression will be translated into

@example
\book @{
  \score @{
    \new Staff @{
      \new Voice @{
        @{ c'4 d' e'2 @}
      @}
    @}
  @}
        \layout @{ @}
        \header @{ @}
@}
@end example

This behavior can be changed by setting the variable
@code{toplevel-music-handler} at toplevel.  The default handler is
defined in the init file @file{../@/scm/@/lily@/.scm}.

@item
A markup text, a verse for example
@example
\markup @{
   2.  The first line verse two.
@}
@end example

Markup texts are rendered above, between or below the scores or music
expressions, wherever they appear.

@cindex variables

@item
A variable, such as
@example
foo = @{ c4 d e d @}
@end example

This can be used later on in the file by entering @code{\foo}.  The
name of a variable should have alphabetic characters only; no
numbers, underscores or dashes.

@end itemize

The following example shows three things that may be entered at
toplevel

@example
\layout @{
  % Don't justify the output
  ragged-right = ##t
@}

\header @{
   title = "Do-re-mi"
@}

@{ c'4 d' e2 @}
@end example


At any point in a file, any of the following lexical instructions can
be entered:

@itemize
@item @code{\version}
@item @code{\include}
@item @code{\sourcefilename}
@item @code{\sourcefileline}
@item
A single-line comment, introduced by a leading @code{%} sign.

@item
A multi-line comment delimited by @code{%@{ .. %@}}.

@end itemize

@cindex whitespace

Whitespace between items in the input stream is generally ignored,
and may be freely omitted or extended to enhance readability.
However, whitespace should always be used in the following
circumstances to avoid errors:

@itemize
@item Around every opening and closing curly bracket.
@item After every command or variable, i.e. every item that
begins with a @code{\} sign.
@item After every item that is to be interpreted as a Scheme
expression, i.e. every item that begins with a @code{#} sign.
@item To separate all elements of a Scheme expression.
@item In @code{lyricmode} to separate all the terms in both
@code{\override} and @code{\set} commands.  In particular, spaces
must be used around the dot and the equals sign in commands like
@code{\override Score . LyricText #'font-size = #5} and before and
after the entire command.

@end itemize


@seealso
Learning Manual:
@rlearning{How LilyPond input files work}.


@node Titles and headers
@section Titles and headers

Almost all printed music includes a title and the composer's name;
some pieces include a lot more information.

@menu
* Creating titles::
* Custom titles::
* Reference to page numbers::
* Table of contents::
@end menu


@node Creating titles
@subsection Creating titles

Titles are created for each @code{\score} block, as well as for the full
input file (or @code{\book} block) and book parts (created by
@code{\bookpart} blocks).

The contents of the titles are taken from the @code{\header} blocks.
The header block for a book supports the following


@table @code
@funindex dedication
@item dedication
The dedicatee of the music, centered at the top of the first page.

@funindex title
@item title
The title of the music, centered just below the dedication.

@funindex subtitle
@item subtitle
Subtitle, centered below the title.

@funindex subsubtitle
@item subsubtitle
Subsubtitle, centered below the subtitle.

@funindex poet
@item poet
Name of the poet, flush-left below the subsubtitle.

@funindex instrument
@item instrument
Name of the instrument, centered below the subsubtitle.  Also
centered at the top of pages (other than the first page).

@funindex composer
@item composer
Name of the composer, flush-right below the subsubtitle.

@funindex meter
@item meter
Meter string, flush-left below the poet.

@funindex arranger
@item arranger
Name of the arranger, flush-right below the composer.

@funindex piece
@item piece
Name of the piece, flush-left below the meter.

@funindex opus
@item opus
Name of the opus, flush-right below the arranger.

@cindex page breaks, forcing
@funindex breakbefore
@item breakbefore
This forces the title to start on a new page (set to ##t or ##f).

@funindex copyright
@item copyright
Copyright notice, centered at the bottom of the first page.  To
insert the copyright symbol, see @ref{Text encoding}.

@funindex tagline
@item tagline
Centered at the bottom of the last page.

@end table

Here is a demonstration of the fields available.  Note that you
may use any @ref{Formatting text}, commands in the header.

@lilypond[quote,verbatim,line-width=11.0\cm]
\paper {
  line-width = 9.0\cm
  paper-height = 10.0\cm
}

\book {
  \header {
    dedication = "dedicated to me"
    title = \markup \center-column { "Title first line" "Title second line,
longer" }
    subtitle = "the subtitle,"
    subsubtitle = #(string-append "subsubtitle LilyPond version "
(lilypond-version))
    poet = "Poet"
    composer =  \markup \center-column { "composer" \small "(1847-1973)" }
    texttranslator = "Text Translator"
    meter = \markup { \teeny "m" \tiny "e" \normalsize "t" \large "e" \huge
"r" }
    arranger = \markup { \fontsize #8.5 "a" \fontsize #2.5 "r" \fontsize
#-2.5 "r" \fontsize #-5.3 "a" \fontsize #7.5 "nger" }
    instrument = \markup \bold \italic "instrument"
    piece = "Piece"
  }

  \score {
    { c'1 }
    \header {
      piece = "piece1"
      opus = "opus1"
    }
  }
  \markup {
      and now...
  }
  \score {
    { c'1 }
    \header {
      piece = "piece2"
      opus = "opus2"
    }
  }
}
@end lilypond

As demonstrated before, you can use multiple @code{\header} blocks.
When same fields appear in different blocks, the latter is used.
Here is a short example.

@example
\header @{
  composer = "Composer"
@}
\header @{
  piece = "Piece"
@}
\score @{
  \new Staff @{ c'4 @}
  \header @{
    piece = "New piece"  % overwrite previous one
  @}
@}
@end example

If you define the @code{\header} inside the @code{\score} block, then
normally only the @code{piece} and @code{opus} headers will be printed.
Note that the music expression must come before the @code{\header}.

@lilypond[quote,verbatim,line-width=11.0\cm]
\score {
  { c'4 }
  \header {
    title = "title"  % not printed
    piece = "piece"
    opus = "opus"
  }
}
@end lilypond

@funindex print-all-headers
@noindent
You may change this behavior (and print all the headers when defining
@code{\header} inside @code{\score}) by using

@example
\paper@{
  print-all-headers = ##t
@}
@end example

@cindex copyright
@cindex tagline

The default footer is empty, except for the first page, where the
@code{copyright} field from @code{\header} is inserted, and the last
page, where @code{tagline} from @code{\header} is added.  The default
tagline is @qq{Music engraving by LilyPond (@var{version})}.@footnote{Nicely
printed parts are good PR for us, so please leave the tagline if you
can.}

Headers may be completely removed by setting them to false.

@example
\header @{
  tagline = ##f
  composer = ##f
@}
@end example


@node Custom titles
@subsection Custom titles

A more advanced option is to change the definitions of the following
variables in the @code{\paper} block.  The init file
@file{../@/ly/@/titling@/-init@/.ly} lists the default layout.

@table @code
@funindex bookTitleMarkup
@item bookTitleMarkup
  This is the title added at the top of the entire output document.
Typically, it has the composer and the title of the piece

@funindex scoreTitleMarkup
@item scoreTitleMarkup
  This is the title put over a @code{\score} block.  Typically, it has
the name of the movement (@code{piece} field).

@funindex oddHeaderMarkup
@item oddHeaderMarkup
  This is the page header for odd-numbered pages.

@funindex evenHeaderMarkup
@item evenHeaderMarkup
  This is the page header for even-numbered pages.  If unspecified,
  the odd header is used instead.

  By default, headers are defined such that the page number is on the
  outside edge, and the instrument is centered.

@funindex oddFooterMarkup
@item oddFooterMarkup
  This is the page footer for odd-numbered pages.

@funindex evenFooterMarkup
@item evenFooterMarkup
  This is the page footer for even-numbered pages.  If unspecified,
  the odd header is used instead.

  By default, the footer has the copyright notice on the first, and
  the tagline on the last page.
@end table


@cindex \paper
@cindex header
@cindex footer
@cindex page layout
@cindex titles

The following definition will put the title flush left, and the
composer flush right on a single line.

@verbatim
\paper {
  bookTitleMarkup = \markup {
   \fill-line {
     \fromproperty #'header:title
     \fromproperty #'header:composer
   }
  }
}
@end verbatim

@node Reference to page numbers
@subsection Reference to page numbers

A particular place of a score can be marked using the @code{\label}
command, either at top-level or inside music.  This label can then be
referred to in a markup, to get the number of the page where the marked
point is placed, using the @code{\page-ref} markup command.

@lilypond[verbatim,line-width=11.0\cm]
\header { tagline = ##f }
\book {
  \label #'firstScore
  \score {
    {
      c'1
      \pageBreak \mark A \label #'markA
      c'
    }
  }

  \markup { The first score begins on page \page-ref #'firstScore "0" "?" }
  \markup { Mark A is on page \page-ref #'markA "0" "?" }
}
@end lilypond

The @code{\page-ref} markup command takes three arguments:
@enumerate
@item the label, a scheme symbol, eg. @code{#'firstScore};
@item a markup that will be used as a gauge to estimate the dimensions
of the markup;
@item a markup that will be used in place of the page number if the label
is not known;
@end enumerate

The reason why a gauge is needed is that, at the time markups are
interpreted, the page breaking has not yet occurred, so the page numbers
are not yet known.  To work around this issue, the actual markup
interpretation is delayed to a later time; however, the dimensions of
the markup have to be known before, so a gauge is used to decide these
dimensions.  If the book has between 10 and 99 pages, it may be "00",
ie. a two digit number.


@predefined
@funindex \label
@code{\label},
@funindex \page-ref
@code{\page-ref}.
@endpredefined


@node Table of contents
@subsection Table of contents
A table of contents is included using the @code{\markuplines \table-of-contents}
command.  The elements which should appear in the table of contents are
entered with the @code{\tocItem} command, which may be used either at
top-level, or inside a music expression.

@verbatim
\markuplines \table-of-contents
\pageBreak

\tocItem \markup "First score"
\score {
  {
    c'  % ...
    \tocItem \markup "Some particular point in the first score"
    d'  % ...
  }
}

\tocItem \markup "Second score"
\score {
  {
    e' % ...
  }
}
@end verbatim

The markups which are used to format the table of contents are defined
in the @code{\paper} block.  The default ones are @code{tocTitleMarkup},
for formatting the title of the table, and @code{tocItemMarkup}, for
formatting the toc elements, composed of the element title and page
number.  These variables may be changed by the user:

@verbatim
\paper {
  %% Translate the toc title into French:
  tocTitleMarkup = \markup \huge \column {
    \fill-line { \null "Table des matières" \null }
    \hspace #1
  }
  %% use larger font size
  tocItemMarkup = \markup \large \fill-line {
    \fromproperty #'toc:text \fromproperty #'toc:page
  }
}
@end verbatim

Note how the toc element text and page number are referred to in
the @code{tocItemMarkup} definition.

New commands and markups may also be defined to build more elaborated
table of contents:
@itemize
@item first, define a new markup variable in the @code{\paper} block
@item then, define a music function which aims at adding a toc element
using this markup paper variable.
@end itemize

In the following example, a new style is defined for entering act names
in the table of contents of an opera:

@verbatim
\paper {
  tocActMarkup = \markup \large \column {
    \hspace #1
    \fill-line { \null \italic \fromproperty #'toc:text \null }
    \hspace #1
  }
}

tocAct =
#(define-music-function (parser location text) (markup?)
   (add-toc-item! 'tocActMarkup text))
@end verbatim

@lilypond[line-width=11.0\cm]
\header { tagline = ##f }
\paper {
  tocActMarkup = \markup \large \column {
    \hspace #1
    \fill-line { \null \italic \fromproperty #'toc:text \null }
    \hspace #1
  }
}

tocAct =
#(define-music-function (parser location text) (markup?)
   (add-toc-item! 'tocActMarkup text))

\book {
  \markuplines \table-of-contents
  \tocAct \markup { Atto Primo }
  \tocItem \markup { Coro. Viva il nostro Alcide }
  \tocItem \markup { Cesare. Presti omai l'Egizzia terra }
  \tocAct \markup { Atto Secondo }
  \tocItem \markup { Sinfonia }
  \tocItem \markup { Cleopatra. V'adoro, pupille, saette d'Amore }
  \markup \null
}
@end lilypond


@seealso
Init files: @file{../@/ly/@/toc@/-init@/.ly}.


@predefined
@funindex \table-of-contents
@code{\table-of-contents},
@funindex \tocItem
@code{\tocItem}.
@endpredefined


@node Working with input files
@section Working with input files

@menu
* Including LilyPond files::
* Different editions from one source::
* Text encoding::
* Displaying LilyPond notation::
@end menu


@node Including LilyPond files
@subsection Including LilyPond files

@funindex \include
@cindex including files

A large project may be split up into separate files.  To refer to
another file, use

@example
\include "otherfile.ly"
@end example

The line @code{\include "otherfile.ly"} is equivalent to pasting the
contents of @file{otherfile.ly} into the current file at the place
where the @code{\include} appears.  For example, in a large
project you might write separate files for each instrument part
and create a @qq{full score} file which brings together the
individual instrument files.  Normally the included file will
define a number of variables which then become available
for use in the full score file.  Tagged sections can be
marked in included files to assist in making them usable in
different places in a score, see @ref{Different editions from
one source}.

Files in the current working directory may be referenced by
specifying just the file name after the @code{\include} command.
Files in other locations may be included by giving either a full
path reference or a relative path reference (but use the UNIX
forward slash, /, rather than the DOS/Windows back slash, \, as the
directory separator.)  For example, if @file{stuff.ly} is located
one directory higher than the current working directory, use

@example
\include "../stuff.ly"
@end example

@noindent
or if the included orchestral parts files are all located in a
subdirectory called @file{parts} within the current directory, use

@example
\include "parts/VI.ly"
\include "parts/VII.ly"
... etc
@end example

Files which are to be included can also contain @code{\include}
statements of their own.  By default, these second-level
@code{\include} statements are not interpreted until they have
been brought into the main file, so the file names they specify
must all be relative to the directory containing the main file,
not the directory containing the included file. However,
this behavior can be changed by passing the option
@code{-drelative-includes} option at the command line
(or by adding @code{#(ly:set-option 'relative-includes #t)}
at the top of the main input file). With @code{relative-includes}
set, the path for each @code{\include} command will be taken
relative to the file containing that command. This behavior is
recommended and it will become the default behavior in a future
version of lilypond.

Files can also be included from a directory in a search path
specified as an option when invoking LilyPond from the command
line.  The included files are then specified using just their
file name.  For example, to compile @file{main.ly} which includes
files located in a subdirectory called @file{parts} by this method,
cd to the directory containing @file{main.ly} and enter

@example
lilypond --include=parts main.ly
@end example

and in main.ly write

@example
\include "VI.ly"
\include "VII.ly"
... etc
@end example

Files which are to be included in many scores may be placed in
the LilyPond directory @file{../ly}.  (The location of this
directory is installation-dependent - see
@rlearning{Other sources of information}).  These files can then
be included simply by naming them on an @code{\include} statement.
This is how the language-dependent files like @file{english.ly} are
included.

LilyPond includes a number of files by default when you start
the program.  These includes are not apparent to the user, but the
files may be identified by running @code{lilypond --verbose} from
the command line.  This will display a list of paths and files that
LilyPond uses, along with much other information.  Alternatively,
the more important of these files are discussed in
@rlearning{Other sources of information}.  These files may be
edited, but changes to them will be lost on installing a new
version of LilyPond.

Some simple examples of using @code{\include} are shown in
@rlearning{Scores and parts}.


@seealso
Learning Manual:
@rlearning{Other sources of information},
@rlearning{Scores and parts}.


@knownissues

If an included file is given a name which is the same as one in
LilyPond's installation files, LilyPond's file from the
installation files takes precedence.



@node Different editions from one source
@subsection Different editions from one source

Several mechanisms are available to facilitate the generation
of different versions of a score from the same music source.
Variables are perhaps most useful for combining lengthy sections
of music and/or annotation in various ways, while tags are more
useful for selecting one from several alternative shorter sections
of music.  Whichever method is used, separating the notation from
the structure of the score will make it easier to change the
structure while leaving the notation untouched.

@menu
* Using variables::
* Using tags::
@end menu

@node Using variables
@unnumberedsubsubsec Using variables

@cindex variables, use of

If sections of the music are defined in variables they can be
reused in different parts of the score, see @rlearning{Organizing
pieces with variables}.  For example, an @notation{a cappella}
vocal score frequently includes a piano reduction of the parts
for rehearsal purposes which is identical to the vocal music, so
the music need be entered only once.  Music from two variables
may be combined on one staff, see @ref{Automatic part combining}.
Here is an example:

@lilypond[verbatim,quote]
sopranoMusic = \relative c'' { a4 b c b8( a)}
altoMusic = \relative g' { e4 e e f }
tenorMusic = \relative c' { c4 b e d8( c) }
bassMusic = \relative c' { a4 gis a d, }
allLyrics = \lyricmode {King of glo -- ry }
<<
  \new Staff = "Soprano" \sopranoMusic
  \new Lyrics \allLyrics
  \new Staff = "Alto" \altoMusic
  \new Lyrics \allLyrics
  \new Staff = "Tenor" {
    \clef "treble_8"
    \tenorMusic
  }
  \new Lyrics \allLyrics
  \new Staff = "Bass" {
    \clef "bass"
    \bassMusic
  }
  \new Lyrics \allLyrics
  \new PianoStaff <<
    \new Staff = "RH" {
      \set Staff.printPartCombineTexts = ##f
      \partcombine
      \sopranoMusic
      \altoMusic
    }
    \new Staff = "LH" {
      \set Staff.printPartCombineTexts = ##f
      \clef "bass"
      \partcombine
      \tenorMusic
      \bassMusic
    }
  >>
>>
@end lilypond

Separate scores showing just the vocal parts or just the piano
part can be produced by changing just the structural statements,
leaving the musical notation unchanged.

For lengthy scores, the variable definitions may be placed in
separate files which are then included, see @ref{Including
LilyPond files}.

@node Using tags
@unnumberedsubsubsec Using tags

@funindex \tag
@funindex \keepWithTag
@funindex \removeWithTag
@cindex tag
@cindex keep tagged music
@cindex remove tagged music

The @code{\tag #'@var{partA}} command marks a music expression
with the name @var{partA}.
Expressions tagged in this way can be selected or filtered out by
name later, using either @code{\keepWithTag #'@var{name}} or
@code{\removeWithTag #'@var{name}}.  The result of applying these filters
to tagged music is as follows:
@multitable @columnfractions .5 .5
@headitem Filter
  @tab Result
@item
Tagged music preceded by @code{\keepWithTag #'@var{name}}
  @tab Untagged music and music tagged with @var{name} is included;
       music tagged with any other tag name is excluded.
@item
Tagged music preceded by @code{\removeWithTag #'@var{name}}
@tab Untagged music and music tagged with any tag name other than
     @var{name} is included; music tagged with @var{name} is
     excluded.
@item
Tagged music not preceded by either @code{\keepWithTag} or
@code{\removeWithTag}
@tab All tagged and untagged music is included.
@end multitable

The arguments of the @code{\tag}, @code{\keepWithTag} and
@code{\removeWithTag} commands should be a symbol
(such as @code{#'score} or @code{#'part}), followed
by a music expression.

In the following example, we see two versions of a piece of music,
one showing trills with the usual notation, and one with trills
explicitly expanded:

@lilypond[verbatim,quote]
music = \relative g' {
  g8. c32 d
  \tag #'trills {d8.\trill }
  \tag #'expand {\repeat unfold 3 {e32 d} }
  c32 d
 }

\score {
  \keepWithTag #'trills \music
}
\score {
  \keepWithTag #'expand \music
}
@end lilypond

@noindent
Alternatively, it is sometimes easier to exclude sections of music:

@lilypond[verbatim,quote]
music = \relative g' {
  g8. c32 d
  \tag #'trills {d8.\trill }
  \tag #'expand {\repeat unfold 3 {e32 d} }
  c32 d
 }

\score {
  \removeWithTag #'expand
  \music
}
\score {
  \removeWithTag #'trills
  \music
}
@end lilypond

Tagged filtering can be applied to articulations, texts, etc. by
prepending

@example
-\tag #'@var{your-tag}
@end example

to an articulation.  For example, this would define a note with a
conditional fingering indication and a note with a conditional
annotation:

@example
c1-\tag #'finger ^4
c1-\tag #'warn ^"Watch!"
@end example

Multiple tags may be placed on expressions with multiple
@code{\tag} entries:

@lilypond[quote,verbatim]
music = \relative c'' {
  \tag #'a \tag #'both { a a a a }
  \tag #'b \tag #'both { b b b b }
}
<<
\keepWithTag #'a \music
\keepWithTag #'b \music
\keepWithTag #'both \music
>>
@end lilypond

Multiple @code{\removeWithTag} filters may be applied to a single
music expression to remove several differently named tagged sections:

@lilypond[verbatim,quote]
music = \relative c'' {
\tag #'A { a a a a }
\tag #'B { b b b b }
\tag #'C { c c c c }
\tag #'D { d d d d }
}
{
\removeWithTag #'B
\removeWithTag #'C
\music
}
@end lilypond

Two or more @code{\keepWithTag} filters applied to a single music
expression will cause @emph{all} tagged sections to be removed, as
the first filter will remove all tagged sections except the one
named, and the second filter will remove even that tagged section.


@seealso
Learning Manual:
@rlearning{Organizing pieces with variables}.

Notation Reference:
@ref{Automatic part combining},
@ref{Including LilyPond files}.


@ignore
@c This warning is more general than this placement implies.
@c Rests are not merged whether or not they come from tagged sections.
@c Should be deleted?  -td

@knownissues

Multiple rests are not merged if you create a score with more
than one tagged section at the same place.

@end ignore

@node Text encoding
@subsection Text encoding

@cindex Unicode
@cindex UTF-8
@cindex non-ASCII characters

LilyPond uses the character repertoire defined by the Unicode
consortium and ISO/IEC 10646.  This defines a unique name and
code point for the character sets used in virtually all modern
languages and many others too.  Unicode can be implemented using
several different encodings.  LilyPond uses the UTF-8 encoding
(UTF stands for Unicode Transformation Format) which represents
all common Latin characters in one byte, and represents other
characters using a variable length format of up to four bytes.

The actual appearance of the characters is determined by the
glyphs defined in the particular fonts available - a font defines
the mapping of a subset of the Unicode code points to glyphs.
LilyPond uses the Pango library to layout and render multi-lingual
texts.

LilyPond does not perform any input-encoding conversions.  This
means that any text, be it title, lyric text, or musical
instruction containing non-ASCII characters, must be encoded in
UTF-8.  The easiest way to enter such text is by using a
Unicode-aware editor and saving the file with UTF-8 encoding.  Most
popular modern editors have UTF-8 support, for example, vim, Emacs,
jEdit, and GEdit do.  All MS Windows systems later than NT use
Unicode as their native character encoding, so even Notepad can
edit and save a file in UTF-8 format.  A more functional
alternative for Windows is BabelPad.

If a LilyPond input file containing a non-ASCII character is not
saved in UTF-8 format the error message

@example
FT_Get_Glyph_Name () error: invalid argument
@end example

will be generated.

Here is an example showing Cyrillic, Hebrew and Portuguese
text:

@lilypond[quote]
%c No verbatim here as the code does not display correctly in PDF
% Cyrillic
bulgarian = \lyricmode {
  Жълтата дюля беше щастлива, че пухът, който цъфна, замръзна като гьон.
}

% Hebrew
hebrew = \lyricmode {
  זה כיף סתם לשמוע איך תנצח קרפד עץ טוב בגן.
}

% Portuguese
portuguese = \lyricmode {
  à vo -- cê uma can -- ção legal
}

\relative  {
  c2 d e f g f e
}
\addlyrics { \bulgarian }
\addlyrics { \hebrew }
\addlyrics { \portuguese }
@end lilypond

To enter a single character for which the Unicode code point is
known but which is not available in the editor being used, use
either @code{\char ##xhhhh} or @code{\char #dddd} within a
@code{\markup} block, where @code{hhhh} is the hexadecimal code for
the character required and @code{dddd} is the corresponding decimal
value.  Leading zeroes may be omitted, but it is usual to specify
all four characters in the hexadecimal representation.  (Note that
the UTF-8 encoding of the code point should @emph{not} be used
after @code{\char}, as UTF-8 encodings contain extra bits indicating
the number of octets.)  Unicode code charts and a character name
index giving the code point in hexadecimal for any character can be
found on the Unicode Consortium website,
@uref{http://www.unicode.org/}.

For example, @code{\char ##x03BE} and @code{\char #958} would both
enter the Unicode U+03BE character, which has the Unicode name
@qq{Greek Small Letter Xi}.

Any Unicode code point may be entered in this way and if all special
characters are entered in this format it is not necessary to save
the input file in UTF-8 format.  Of course, a font containing all
such encoded characters must be installed and available to LilyPond.

The following example shows Unicode hexadecimal values being entered
in four places -- in a rehearsal mark, as articulation text, in
lyrics and as stand-alone text below the score:

@lilypond[quote,verbatim]
\score {
  \relative c'' {
    c1 \mark \markup { \char ##x03EE }
    c1_\markup { \tiny { \char ##x03B1 " to " \char ##x03C9 } }
  }
  \addlyrics { O \markup { \concat{ Ph \char ##x0153 be! } } }
}
\markup { "Copyright 2008--2010" \char ##x00A9 }
@end lilypond

@cindex copyright sign

To enter the copyright sign in the copyright notice use:

@example
\header @{
  copyright = \markup @{ \char ##x00A9 "2008" @}
@}
@end example

@node Displaying LilyPond notation
@subsection Displaying LilyPond notation

@funindex \displayLilyMusic
Displaying a music expression in LilyPond notation can be
done using the music function @code{\displayLilyMusic}.  For example,

@example
@{
  \displayLilyMusic \transpose c a, @{ c e g a bes @}
@}
@end example

will display

@example
@{ a, cis e fis g @}
@end example

By default, LilyPond will print these messages to the console along
with all the other messages.  To split up these messages and save
the results of @code{\display@{STUFF@}}, redirect the output to
a file.

@c TODO What happens under Windows?

@example
lilypond file.ly >display.txt
@end example



@node Controlling output
@section Controlling output

@menu
* Extracting fragments of music::
* Skipping corrected music::
* Alternative output formats::
@end menu

@node Extracting fragments of music
@subsection Extracting fragments of music

It is possible to quote small fragments of a large score directly from
the output.  This can be compared to clipping a piece of a paper score
with scissors.

This is done by defining the measures that need to be cut out
separately.  For example, including the following definition


@verbatim
\layout {
  clip-regions
  = #(list
      (cons
       (make-rhythmic-location 5 1 2)
       (make-rhythmic-location 7 3 4)))
}
@end verbatim

@noindent
will extract a fragment starting halfway the fifth measure, ending in
the seventh measure.  The meaning of @code{5 1 2} is: after a 1/2 note
in measure 5, and @code{7 3 4} after 3 quarter notes in measure 7.

More clip regions can be defined by adding more pairs of
rhythmic-locations to the list.

In order to use this feature, LilyPond must be invoked with
@code{-dclip-systems}.  The clips are output as EPS files, and are
converted to PDF and PNG if these formats are switched on as well.

For more information on output formats, see @rprogram{Invoking lilypond}.

@node Skipping corrected music
@subsection Skipping corrected music


@funindex skipTypesetting
@funindex showFirstLength
@funindex showLastLength

When entering or copying music, usually only the music near the end (where
you
are adding notes) is interesting to view and correct.  To speed up
this correction process, it is possible to skip typesetting of all but
the last few measures.  This is achieved by putting

@verbatim
showLastLength = R1*5
\score { ... }
@end verbatim

@noindent
in your source file.  This will render only the last 5 measures
(assuming 4/4 time signature) of every @code{\score} in the input
file.  For longer pieces, rendering only a small part is often an order
of magnitude quicker than rendering it completely.  When working on the
beginning of a score you have already typeset (e.g. to add a new part),
the @code{showFirstLength} property may be useful as well.

Skipping parts of a score can be controlled in a more fine-grained
fashion with the property @code{Score.skipTypesetting}.  When it is
set, no typesetting is performed at all.

This property is also used to control output to the MIDI file.  Note that
it skips all events, including tempo and instrument changes.  You have
been warned.

@lilypond[quote,fragment,ragged-right,verbatim]
\relative c'' {
  c8 d
  \set Score.skipTypesetting = ##t
  e e e e e e e e
  \set Score.skipTypesetting = ##f
  c d b bes a g c2 }
@end lilypond

In polyphonic music, @code{Score.skipTypesetting} will affect all
voices and staves, saving even more time.

@node Alternative output formats
@subsection Alternative output formats

@cindex scalable vector graphics output
@cindex SVG output
@cindex encapsulated postscript output
@cindex EPS output

The default output formats for the printed score are Portable
Document Format (PDF) and PostScript (PS).  Scalable Vector
Graphics (SVG), Encapsulated PostScript (EPS) and Portable
Network Graphics (PNG) output formats are also available through
command line options, see @rprogram{Command line options for
lilypond}.


@node MIDI output
@section MIDI output

@cindex Sound
@cindex MIDI

MIDI (Musical Instrument Digital Interface) is a standard for
connecting and controlling digital instruments.  A MIDI file is a
series of notes in a number of tracks.  It is not an actual
sound file; you need special software to translate between the
series of notes and actual sounds.

Pieces of music can be converted to MIDI files, so you can listen to
what was entered.  This is convenient for checking the music; octaves
that are off or accidentals that were mistyped stand out very much
when listening to the MIDI output.

@c TODO Check this
The midi output allocates a channel for each staff, and one for global
settings.  Therefore the midi file should not have more than 15 staves
(or 14 if you do not use drums).  Other staves will remain silent.

@menu
* Creating MIDI files::
* MIDI block::
* What goes into the MIDI output?::
* Repeats in MIDI::
* Controlling MIDI dynamics::
* Percussion in MIDI::
@end menu

@node Creating MIDI files
@subsection Creating MIDI files

To create a MIDI output file from a LilyPond input file, add a
@code{\midi} block to a score, for example,

@example
\score @{
  @var{...music...}
  \midi @{ @}
@}
@end example

If there is a @code{\midi} block in a @code{\score} with no
@code{\layout} block, only MIDI output will be produced.  When
notation is needed too, a @code{\layout} block must be also be
present.

@example
\score @{
  @var{...music...}
  \midi @{ @}
  \layout @{ @}
@}
@end example

Pitches, rhythms, ties, dynamics, and tempo changes are interpreted
and translated correctly to the MIDI output.  Dynamic marks,
crescendi and decrescendi translate into MIDI volume levels.
Dynamic marks translate to a fixed fraction of the available MIDI
volume range.  Crescendi and decrescendi make the volume vary
linearly between their two extremes.  The effect of dynamic markings
on the MIDI output can be removed completely, see @ref{MIDI block}.

The initial tempo and later tempo changes can be specified
with the @code{\tempo} command within the music notation.  These
are reflected in tempo changes in the MIDI output.  This command
will normally result in the metronome mark being printed, but this
can be suppressed, see @ref{Metronome marks}.  An alternative way
of specifying the inital or overall MIDI tempo is described below,
see @ref{MIDI block}.

Due to some limitations on Windows, the default extension for
MIDI files on Windows is @code{.mid}. Other operating systems still
use the extension @code{.midi}. If a different extension is preferred,
insert the following line at the top-level of the input file,
before the start of any @code{\book}, @code{\bookpart} or @code{\score} blocks:

@example
#(ly:set-option 'midi-extension "midi")
@end example

The line above will set the default extension for MIDI files to
@code{.midi}.

Alternatively, this option can also be supplied on the command line:

@example
lilypond … -dmidi-extension=midi lilyFile.ly
@end example


@unnumberedsubsubsec Instrument names

@cindex instrument names
@funindex Staff.midiInstrument

The MIDI instrument to be used is specified by setting the
@code{Staff.midiInstrument} property to the instrument name.
The name should be chosen from the list in @ref{MIDI instruments}.

@example
\new Staff @{
  \set Staff.midiInstrument = #"glockenspiel"
  @var{...notes...}
@}
@end example

@example
\new Staff \with @{midiInstrument = #"cello"@} @{
  @var{...notes...}
@}
@end example

If the selected instrument does not exactly match an instrument from
the list of MIDI instruments, the Grand Piano (@code{"acoustic grand"})
instrument is used.


@snippets

@lilypondfile[verbatim,lilyquote,ragged-right,texidoc,doctitle]
{changing-midi-output-to-one-channel-per-voice.ly}

@knownissues

@c In 2.11 the following no longer seems to be a problem -td
@ignore
Unterminated (de)crescendos will not render properly in the midi file,
resulting in silent passages of music.  The workaround is to explicitly
terminate the (de)crescendo.  For example,

@example
@{ a\< b c d\f @}
@end example

@noindent
will not work properly but

@example
@{ a\< b c d\!\f @}
@end example

@noindent
will.
@end ignore

Changes in the MIDI volume take place only on starting a note, so
crescendi and decrescendi cannot affect the volume of a
single note.

Not all midi players correctly handle tempo changes in the midi
output.  Players that are known to work include MS Windows Media
Player and @uref{http://@/timidity@/.sourceforge@/.net/,timidity}.

@node MIDI block
@subsection MIDI block
@cindex MIDI block

A @code{\midi} block must appear within a score block if MIDI output
is required.  It is analogous to the layout block, but somewhat
simpler.  Often, the @code{\midi} block is left empty, but it
can contain context rearrangements, new context definitions or code
to set the values of properties.  For example, the following will
set the initial tempo exported to a MIDI file without causing a tempo
indication to be printed:

@example
\score @{
  @var{...music...}
  \midi @{
    \context @{
      \Score
      tempoWholesPerMinute = #(ly:make-moment 72 4)
    @}
  @}
@}
@end example

In this example the tempo is set to 72 quarter note
beats per minute.  This kind of tempo specification cannot take
a dotted note length as an argument.  If one is required, break
the dotted note into smaller units.  For example, a tempo of 90
dotted quarter notes per minute can be specified as 270 eighth
notes per minute:

@example
tempoWholesPerMinute = #(ly:make-moment 270 8)
@end example

@cindex MIDI context definitions

Context definitions follow precisely the same syntax as those
within a @code{\layout} block.  Translation modules for sound are
called performers.  The contexts for MIDI output are defined in
@file{../@/ly/@/performer@/-init@/.ly},
see @rlearning{Other sources of information}.
For example, to remove the effect of dynamics
from the MIDI output, insert the following lines in the
@code{\midi@{ @}} block.

@example
\midi @{
  ...
  \context @{
    \Voice
    \remove "Dynamic_performer"
  @}
@}
@end example

MIDI output is created only when a @code{\midi} block is included
within a score block defined with a @code{\score} command.  If it
is placed within an explicitly instantiated score context (i.e.
within a @code{\new Score} block) the file will fail.  To solve
this, enclose the @code{\new Score} and the @code{\midi} commands
in a @code{\score} block.

@example
\score @{
  \new Score @{ @dots{}notes@dots{} @}
  \midi @{ @}
@}
@end example

@node What goes into the MIDI output?
@subsection What goes into the MIDI output?

@c TODO Check grace notes - timing is suspect?

@unnumberedsubsubsec Supported in MIDI

@cindex Pitches in MIDI
@cindex MIDI, Pitches
@cindex Quarter tones in MIDI
@cindex MIDI, quarter tones
@cindex Microtones in MIDI
@cindex MIDI, microtones
@cindex Chord names in MIDI
@cindex MIDI, chord names
@cindex Rhythms in MIDI
@cindex MIDI, Rhythms
@c TODO etc

The following items of notation are reflected in the MIDI output:

@itemize
@item Pitches
@item Microtones (See @ref{Accidentals}. Rendering needs a
player that supports pitch bend.)
@item Chords entered as chord names
@item Rhythms entered as note durations, including tuplets
@item Tremolos entered without @q{@code{:}[@var{number}]}
@item Ties
@item Dynamic marks
@item Crescendi, decrescendi over multiple notes
@item Tempo changes entered with a tempo marking
@item Lyrics
@end itemize

@unnumberedsubsubsec Unsupported in MIDI

@c TODO index as above

The following items of notation have no effect on the MIDI output:

@itemize
@item Rhythms entered as annotations, e.g. swing
@item Tempo changes entered as annotations with no tempo marking
@item Staccato and other articulations and ornamentations
@item Slurs and Phrasing slurs
@item Crescendi, decrescendi over a single note
@item Tremolos entered with @q{@code{:}[@var{number}]}
@item Figured bass
@item Microtonal chords
@end itemize


@node Repeats in MIDI
@subsection Repeats in MIDI

@cindex repeats in MIDI
@funindex \unfoldRepeats

With a few minor additions, all types of repeats can be represented
in the MIDI output.  This is achieved by applying the
@code{\unfoldRepeats} music function.  This function changes all
repeats to unfold repeats.

@lilypond[quote,verbatim]
\unfoldRepeats {
  \repeat tremolo 8 {c'32 e' }
  \repeat percent 2 { c''8 d'' }
  \repeat volta 2 {c'4 d' e' f'}
  \alternative {
    { g' a' a' g' }
    {f' e' d' c' }
  }
}
\bar "|."
@end lilypond

When creating a score file using @code{\unfoldRepeats} for MIDI,
it is necessary to make two @code{\score} blocks: one for MIDI
(with unfolded repeats) and one for notation (with volta, tremolo,
and percent repeats).  For example,

@example
\score @{
  @var{..music..}
  \layout @{ .. @}
@}
\score @{
  \unfoldRepeats @var{..music..}
  \midi @{ .. @}
@}
@end example

@node Controlling MIDI dynamics
@subsection Controlling MIDI dynamics

MIDI dynamics are implemented by the Dynamic_performer which lives
by default in the Voice context.  It is possible to control the
overall MIDI volume, the relative volume of dynamic markings and
the relative volume of different instruments.

@unnumberedsubsubsec Dynamic marks

Dynamic marks are translated to a fixed fraction of the available
MIDI volume range.  The default fractions range from 0.25 for
@notation{ppppp} to 0.95 for @notation{fffff}.  The set of dynamic
marks and the associated fractions can be seen in
@file{../@/scm/@/midi.scm}, see @rlearning{Other sources of information}.
This set of fractions may be changed or extended by providing a
function which takes a dynamic mark as its argument and returns the
required fraction, and setting
@code{Score.dynamicAbsoluteVolumeFunction} to this function.

For example, if a @notation{rinforzando} dynamic marking,
@code{\rfz}, is required, this will not by default
have any effect on the MIDI volume, as this dynamic marking is not
included in the default set.  Similarly, if a new dynamic marking
has been defined with @code{make-dynamic-script} that too will not
be included in the default set.  The following example shows how the
MIDI volume for such dynamic markings might be added.  The Scheme
function sets the fraction to 0.9 if a dynamic mark of rfz is
found, or calls the default function otherwise.

@lilypond[verbatim,quote]
#(define (myDynamics dynamic)
    (if (equal? dynamic "rfz")
      0.9
      (default-dynamic-absolute-volume dynamic)))

\score {
  \new Staff {
    \set Staff.midiInstrument = #"cello"
    \set Score.dynamicAbsoluteVolumeFunction = #myDynamics
    \new Voice {
       \relative c'' {
         a\pp b c-\rfz
       }
    }
  }
  \layout {}
  \midi {}
}
@end lilypond

Alternatively, if the whole table of fractions needs to be
redefined, it would be better to use the
@notation{default-dynamic-absolute-volume} procedure in
@file{../@/scm/@/midi.scm} and the associated table as a model.
The final example in this section shows how this might be done.

@unnumberedsubsubsec Overall MIDI volume

The minimum and maximum overall volume of MIDI dynamic markings is
controlled by setting the properties @code{midiMinimumVolume} and
@code{midiMaximumVolume} at the @code{Score} level.  These
properties have an effect only on dynamic marks, so if they
are to apply from the start of the score a dynamic mark must be
placed there.  The fraction corresponding to each dynamic mark is
modified with this formula

@example
midiMinimumVolume + (midiMaximumVolume - midiMinimumVolume) * fraction
@end example

In the following example the dynamic range of the overall MIDI
volume is limited to the range 0.2 - 0.5.

@lilypond[verbatim,quote]
\score {
  <<
    \new Staff {
      \key g \major
      \time 2/2
      \set Staff.midiInstrument = #"flute"
      \new Voice \relative c''' {
        r2 g\mp g fis ~
        fis4 g8 fis e2 ~
        e4 d8 cis d2
      }
    }
    \new Staff {
      \key g \major
      \set Staff.midiInstrument = #"clarinet"
      \new Voice \relative c'' {
        b1\p a2. b8 a
        g2. fis8 e
        fis2 r
      }
    }
  >>
  \layout { }
  \midi {
    \context {
      \Score
      tempoWholesPerMinute = #(ly:make-moment 72 2)
      midiMinimumVolume = #0.2
      midiMaximumVolume = #0.5
    }
  }
}
@end lilypond

@unnumberedsubsubsec Equalizing different instruments (i)

If the minimum and maximum MIDI volume properties are set in
the @code{Staff} context the relative volumes of the MIDI
instruments can be controlled.  This gives a basic instrument
equalizer, which can enhance the quality of the MIDI output
remarkably.

In this example the volume of the clarinet is reduced relative
to the volume of the flute.  There must be a dynamic
mark on the first note of each instrument for this to work
correctly.

@lilypond[verbatim,quote]
\score {
  <<
    \new Staff {
      \key g \major
      \time 2/2
      \set Staff.midiInstrument = #"flute"
      \set Staff.midiMinimumVolume = #0.7
      \set Staff.midiMaximumVolume = #0.9
      \new Voice \relative c''' {
        r2 g\mp g fis ~
        fis4 g8 fis e2 ~
        e4 d8 cis d2
      }
    }
    \new Staff {
      \key g \major
      \set Staff.midiInstrument = #"clarinet"
      \set Staff.midiMinimumVolume = #0.3
      \set Staff.midiMaximumVolume = #0.6
      \new Voice \relative c'' {
        b1\p a2. b8 a
        g2. fis8 e
        fis2 r
      }
    }
  >>
  \layout { }
  \midi {
    \context {
      \Score
      tempoWholesPerMinute = #(ly:make-moment 72 2)
    }
  }
}
@end lilypond

@unnumberedsubsubsec Equalizing different instruments (ii)

If the MIDI minimum and maximum volume properties are not set
LilyPond will, by default, apply a small degree of equalization
to a few instruments.  The instruments and the equalization
applied are shown in the table @notation{instrument-equalizer-alist}
in @file{../@/scm/@/midi.scm}.

This basic default equalizer can be replaced by setting
@code{instrumentEqualizer} in the @code{Score} context to a new
Scheme procedure which accepts a MIDI instrument name as its only
argument and returns a pair of fractions giving the minimum and
maximum volumes to be applied to that instrument.  This replacement
is done in the same way as shown for resetting the
@code{dynamicAbsoluteVolumeFunction} at the start of this section.
The default equalizer, @notation{default-instrument-equalizer}, in
@file{../@/scm/@/midi.scm} shows how such a procedure might be written.

The following example sets the relative flute and clarinet volumes
to the same values as the previous example.

@lilypond[verbatim,quote]
#(define my-instrument-equalizer-alist '())

#(set! my-instrument-equalizer-alist
  (append
    '(
      ("flute" . (0.7 . 0.9))
      ("clarinet" . (0.3 . 0.6)))
    my-instrument-equalizer-alist))

#(define (my-instrument-equalizer s)
  (let ((entry (assoc s my-instrument-equalizer-alist)))
    (if entry
      (cdr entry))))

\score {
  <<
    \new Staff {
      \key g \major
      \time 2/2
      \set Score.instrumentEqualizer = #my-instrument-equalizer
      \set Staff.midiInstrument = #"flute"
      \new Voice \relative c''' {
        r2 g\mp g fis ~
        fis4 g8 fis e2 ~
        e4 d8 cis d2
      }
    }
    \new Staff {
      \key g \major
      \set Staff.midiInstrument = #"clarinet"
      \new Voice \relative c'' {
        b1\p a2. b8 a
        g2. fis8 e
        fis2 r
      }
    }
  >>
  \layout { }
  \midi {
    \context {
      \Score
      tempoWholesPerMinute = #(ly:make-moment 72 2)
    }
  }
}
@end lilypond

@ignore
@c Delete when satisfied this is adequately covered elsewhere -td

@n ode Microtones in MIDI
@s ubsection Microtones in MIDI

@cindex microtones in MIDI

Microtones consisting of half sharps and half flats are exported
to the MIDI file and render correctly in MIDI players which support
pitch bending.  See @ref{Note names in other languages}.  Here is
an example showing all the half sharps and half flats.  It can be
copied out and compiled to test microtones in your MIDI player.

@lilypond[verbatim,quote]
\score {
  \relative c' {
    c cih cis cisih
    d dih ees eeh
    e eih f fih
    fis fisih g gih
    gis gisih a aih
    bes beh b bih
  }
  \layout {}
  \midi {}
}
@end lilypond
@end ignore


@node Percussion in MIDI
@subsection Percussion in MIDI

Percussion instruments are generally notated in a @code{DrumStaff}
context and when notated in this way they are outputted correctly
to MIDI channel@tie{}10, but some pitched percussion instruments,
like the xylophone, marimba, vibraphone, timpani, etc., are
treated like @qq{normal} instruments and music for these instruments
should be entered in a normal @code{Staff} context, not a
@code{DrumStaff} context, to obtain the correct MIDI output.

Some non-pitched percussion sounds included in the general MIDI
standard, like melodic tom, taiko drum, synth drum, etc., cannot
be reached via MIDI channel@tie{}10, so the notation for such
instruments should also be entered in a normal @code{Staff}
context, using suitable normal pitches.

Many percussion instruments are not included in the general MIDI
standard, e.g. castanets.  The easiest, although unsatisfactory,
method of producing some MIDI output when writing for such
instruments is to substitute the nearest sound from the standard
set.

@c TODO Expand with examples, and any other issues

@knownissues

Because the general MIDI standard does not contain rim shots, the
sidestick is used for this purpose instead.