Remove duplicate info.

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

@c -*- coding: latin-1; mode: texinfo; -*-
@c This file is part of lilypond.tely

@c A menu is needed before every deeper *section nesting of @node's; run 
@c     M-x texinfo-all-menus-update
@c to automatically fill in these menus before saving changes

@node Output formats
@chapter Output formats

This is a placeholder until I can write a nice intro for this chapter.

@menu
* Paper output::                
* Sound output::                
@end menu


@node Paper output
@section Paper output

The global paper layout is determined by three factors: the page layout, the
line breaks, and the spacing.  These all influence each other.  The
choice of spacing determines how densely each system of music is set.
This influences where line breaks are chosen, and thus ultimately, how
many pages a piece of music takes.

Globally spoken, this procedure happens in three steps: first,
flexible distances (``springs'') are chosen, based on durations.  All
possible line breaking combinations are tried, and the one with the
best results -- a layout that has uniform density and requires as
little stretching or cramping as possible -- is chosen.

After spacing and linebreaking, the systems are distributed across
pages, taking into account the size of the page, and the size of the
titles.



@menu
* Setting global staff size::   
* Paper size::                  
* Page layout::                 
* Vertical spacing::            
* Vertical spacing of piano staves::  
* Horizontal spacing::          
* Line length::                 
* Line breaking::               
* Page breaking::               
* Multiple movements::          
* Creating titles::             
@end menu


@node Setting global staff size
@subsection Setting global staff size

@cindex font size, setting
@cindex staff size, setting
@cindex @code{layout} file

To set the global staff size, use @code{set-global-staff-size}.

@example
#(set-global-staff-size 14)
@end example

@noindent
This sets the global default size to 14pt staff height and scales all
fonts accordingly.

The Feta font provides musical symbols at eight different
sizes.  Each font is tuned for a different staff size: at a smaller size
the font becomes heavier, to match the relatively heavier staff lines.
The recommended font sizes are listed in the following table:

@quotation
@multitable @columnfractions .15 .2 .22 .2

@item @b{font name}
@tab @b{staff height (pt)}
@tab @b{staff height (mm)}
@tab @b{use}

@item feta11
@tab 11.22
@tab 3.9 
@tab pocket scores

@item feta13
@tab 12.60
@tab 4.4
@tab
 
@item feta14
@tab 14.14
@tab 5.0
@tab 

@item feta16
@tab 15.87
@tab 5.6
@tab 

@item feta18
@tab 17.82
@tab 6.3
@tab song books

@item feta20
@tab 20
@tab 7.0
@tab standard parts 

@item feta23
@tab 22.45 
@tab 7.9
@tab 

@item feta26
@tab 25.2 
@tab 8.9
@tab
@c modern rental material?

@end multitable
@end quotation

These fonts are available in any sizes.  The context property
@code{fontSize} and the layout property @code{staff-space} (in
@internalsref{StaffSymbol}) can be used to tune the size for individual
staves.  The sizes of individual staves are relative to the global size.

@example

@end example

@seealso

This manual: @ref{Selecting font sizes}.


@node Paper size
@subsection Paper size

@cindex paper size
@cindex page size
@cindex @code{papersize}

To change the paper size, there are two commands,
@example
#(set-default-paper-size "a4")
\paper @{
  #(set-paper-size "a4")
@}
@end example

The first command sets the size of all pages.  The second command sets the size
of the pages that the @code{\paper} block applies to -- if the @code{\paper}
block is at the top of the file, then it will apply to all pages.  If the
@code{\paper} block is inside a @code{\score}, then the paper size will only
apply to that score.

The following paper sizes are supported: @code{a6}, @code{a5}, @code{a4},
@code{a3}, @code{legal}, @code{letter}, @code{tabloid}.

@cindex orientation
@cindex landscape

If the symbol @code{landscape} is supplied as an argument to
@code{set-default-paper-size}, the pages will be rotated by 90 degrees,
and wider line widths will be set correspondingly.

@example
#(set-default-paper-size "a6" 'landscape)
@end example 


@node Page layout
@subsection Page layout

@cindex page layout
@cindex margins
@cindex header, page
@cindex footer, page

LilyPond will do page layout, set margins, and add headers and
footers to each page.

The default layout responds to the following settings in the
@code{\paper} block.

@cindex \paper

@quotation
@table @code
@item firstpagenumber
The value of the page number of the first page.  Default is@tie{}1.

@item printfirstpagenumber
If set to true, will print the page number in the first page.  Default is
false.

@item hsize
The width of the page.

@item vsize
The height of the page.

@item topmargin
Margin between header and top of the page.

@item bottommargin
Margin between footer and bottom of the page.

@item leftmargin
Margin between the left side of the page and the beginning of the music.

@item linewidth
The length of the systems.

@item headsep
Distance between the top-most music system and the page header.

@item footsep
Distance between the bottom-most music system and the page footer.

@item raggedbottom
If set to true, systems will not be spread across the page.

This should be set false for pieces that have only two or three
systems per page, for example orchestral scores.
 
@item raggedlastbottom
If set to false, systems will be spread to fill the last page.

Pieces that amply fill two pages or more should have this set to
true.

@item betweensystemspace
This dimensions determines the distance between systems.  It is the
ideal distance between the center of the bottom staff of one system
and the center of the top staff of the next system.

Increasing this will provide a more even appearance of the page at the
cost of using more vertical space.

@item betweensystempadding
This dimension is the minimum amount of white space that will always
be present between the bottom-most symbol of one system, and the
top-most of the next system.

Increasing this will put systems whose bounding boxes almost touch
farther apart.

@item aftertitlespace
Amount of space between the title and the first system.

@item beforetitlespace 
Amount of space between the last system of the previous piece and the
title of the next.

@item betweentitlespace
Amount of space between consecutive titles (e.g., the title of the
book and the title of a piece).

@item systemSeparatorMarkup
This contains a markup object, which will be inserted between
systems.  This is often used for orchestral scores.

The markup command @code{\slashSeparator} is provided as a sensible
default,  for example

@lilypond[raggedright]
\paper {
  systemSeparatorMarkup = \slashSeparator
}

\relative { c1 \break c1 }
@end lilypond


@end table
@end quotation

Example:

@example
\paper@{
  hsize = 2\cm
  topmargin = 3\cm
  bottommargin = 3\cm
  raggedlastbottom = ##t
@}
@end example

You can also define these values in Scheme.  In that case @code{mm},
@code{in}, @code{pt}, and @code{cm} are variables defined in
@file{paper-defaults.ly} with values in millimeters.  That's why the
value has to be multiplied in the example

@example
\paper @{
  #(define bottommargin (* 2 cm)) 
@}
@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 ``Music engraving by LilyPond (@var{version})''.@footnote{Nicely
printed parts are good PR for us, so please leave the tagline if you
can.}

The header and footer are created by the functions @code{make-footer}
and @code{make-header}, defined in @code{\paper}.  The default
implementations are in @file{scm/@/page@/-layout@/.scm}.

The page layout itself is done by two functions in the
@code{\paper} block, @code{page-music-height} and
@code{page-make-stencil}.  The former tells the line-breaking algorithm
how much space can be spent on a page, the latter creates the actual
page given the system to put on it.


@refbugs

The option rightmargin is defined but doesn't set the right margin
yet.  The value for the right margin has to be defined adjusting the
values of the leftmargin and linewidth.

The default page header puts the page number and the @code{instrument}
field from the @code{\header} block on a line.


@node Vertical spacing
@subsection Vertical spacing

@cindex vertical spacing
@cindex distance between staves
@cindex staff distance
@cindex between staves, distance
@cindex staves per page
@cindex space between staves

The height of each system is determined automatically.  To prevent
systems from bumping into each other, some minimum distances are set.
By changing these, you can put staves closer together, and thus put
more systems onto one page.

Normally staves are stacked vertically.  To make staves maintain a
distance, their vertical size is padded.  This is done with the
property @code{minimumVerticalExtent}.  It takes a pair of numbers, so
if you want to make it smaller than its default @code{#'(-4 . 4)},
then you could set

@example
\set Staff.minimumVerticalExtent = #'(-3 . 3)
@end example

@noindent
This sets the vertical size of the current staff to 3 staff spaces on
either side of the center staff line.  The argument of
@code{minimumVerticalExtent} is interpreted as an interval, where the
center line is the 0, so the first number is generally negative.  The
staff can be made larger at the bottom by setting it to @code{(-6 . 4)}. 

To change the amount of space between systems, use
@code{betweensystemspace}.  A score with only one staff is still
considered to have systems, so setting @code{betweensystemspace}
will be much more useful than changing @code{minimumVerticalExtent}.

@example
\layout @{
  betweensystemspace = 10\mm
@}
@end example


@seealso

Internals: Vertical alignment of staves is handled by the
@internalsref{VerticalAlignment} object.

@refbugs

@code{minimumVerticalExtent} is syntactic sugar for setting
@code{minimum-Y-extent} of the @internalsref{VerticalAxisGroup} of the
current context.  It can only be changed score wide.




@node Vertical spacing of piano staves
@subsection Vertical spacing of piano staves

The distance between staves of a @internalsref{PianoStaff} cannot be
computed during formatting.  Rather, to make cross-staff beaming work
correctly, that distance has to be fixed beforehand.
 
The distance of staves in a @code{PianoStaff} is set with the
@code{forced-distance} property of the
@internalsref{VerticalAlignment} object, created in
@internalsref{PianoStaff}.

It can be adjusted as follows
@example
\new PianoStaff \with @{
  \override VerticalAlignment #'forced-distance = #7
@} @{
  ...
@}
@end example

@noindent
This would bring the staves together at a distance of 7 staff spaces,
measured from the center line of each staff.

The difference is demonstrated in the following example,
@lilypond[quote,verbatim]
\relative <<
  \new PianoStaff \with {
    \override VerticalAlignment #'forced-distance = #7
  } <<
    \new Staff { c1 }
    \new Staff { c }
  >>
  \new PianoStaff <<
    \new Staff { c }
    \new Staff { c }
  >>
>>    
@end lilypond



@refbugs

@code{forced-distance} cannot be changed per system.


@node Horizontal spacing
@subsection Horizontal Spacing

The spacing engine translates differences in durations into
stretchable distances (``springs'') of differring lengths.  Longer
durations get more space, shorter durations get less.  The shortest
durations get a fixed amount of space (which is controlled by
@code{shortest-duration-space} in the @internalsref{SpacingSpanner} object). 
The longer the duration, the more space it gets: doubling a
duration adds a fixed amount (this amount is controlled by
@code{spacing-increment}) of space to the note.

For example, the following piece contains lots of half, quarter, and
8th notes; the eighth note is followed by 1 note head width (NHW). 
The quarter note is followed by 2 NHW, the half by 3 NHW, etc.

@lilypond[quote,fragment,verbatim,relative=1]
c2 c4. c8 c4. c8 c4. c8 c8
c8 c4 c4 c4
@end lilypond

Normally, @code{spacing-increment} is set to 1.2 staff space, which is
approximately the width of a note head, and
@code{shortest-duration-space} is set to 2.0, meaning that the
shortest note gets 2.4 staff space (2.0 times the
@code{spacing-increment}) of horizontal space.  This space is counted
from the left edge of the symbol, so the shortest notes are generally
followed by one NHW of space.

If one would follow the above procedure exactly, then adding a single
32nd note to a score that uses 8th and 16th notes, would widen up the
entire score a lot.  The shortest note is no longer a 16th, but a 32nd,
thus adding 1 NHW to every note.  To prevent this, the shortest
duration for spacing is not the shortest note in the score, but rather
the one which occurs most frequently.


The most common shortest duration is determined as follows: in every
measure, the shortest duration is determined.  The most common shortest
duration is taken as the basis for the spacing, with the stipulation
that this shortest duration should always be equal to or shorter than
an 8th note.  The shortest duration is printed when you run
@code{lilypond} with the @code{--verbose} option.

These durations may also be customized.  If you set the
@code{common-shortest-duration} in @internalsref{SpacingSpanner}, then
this sets the base duration for spacing.  The maximum duration for this
base (normally an 8th), is set through @code{base-shortest-duration}.

@cindex @code{common-shortest-duration}
@cindex @code{base-shortest-duration}
@cindex @code{stem-spacing-correction}
@cindex @code{spacing}

Notes that are even shorter than the common shortest note are
followed by a space that is proportional to their duration relative to
the common shortest note.  So if we were to add only a few 16th notes
to the example above, they would be followed by half a NHW:

@lilypond[quote,fragment,verbatim,relative=2]
c2 c4. c8 c4. c16[ c] c4. c8 c8 c8 c4 c4 c4
@end lilypond


In the introduction (see @ref{Engraving}), it was explained that stem
directions influence spacing.  This is controlled with the
@code{stem-spacing-correction} property in the
@internalsref{NoteSpacing}, object.  These are generated for every
@internalsref{Voice} context.  The @code{StaffSpacing} object
(generated in @internalsref{Staff} context) contains the same property
for controlling the stem/bar line spacing.  The following example shows
these corrections, once with default settings, and once with
exaggerated corrections:

@lilypond[quote,raggedright]
{
  c'4 e''4 e'4 b'4 |
  b'4 e''4 b'4 e''4|
  \override Staff.NoteSpacing #'stem-spacing-correction = #1.5
  \override Staff.StaffSpacing #'stem-spacing-correction = #1.5
  c'4 e''4 e'4 b'4 |
  b'4 e''4 b'4 e''4|      
}
@end lilypond


@seealso

Internals: @internalsref{SpacingSpanner}, @internalsref{NoteSpacing},
@internalsref{StaffSpacing}, @internalsref{SeparationItem}, and
@internalsref{SeparatingGroupSpanner}.

@refbugs

Spacing is determined on a score wide basis.  If you have a score that
changes its character (measured in durations) halfway during the
score, the part containing the longer durations will be spaced too
widely.

There is no convenient mechanism to manually override spacing.  The
following work-around may be used to insert extra space into a score.
@example
 \once \override Score.SeparationItem #'padding = #1
@end example

No work-around exists for decreasing the amount of space.

@node Line length
@subsection Line length

@cindex page breaks
@cindex breaking pages

@cindex @code{indent}
@cindex @code{linewidth}

@c Although linewidth can be set in \layout, it should be set in paper
@c block, to get page layout right.
@c Setting indent in \paper block makes not much sense, but it works.

@c Bit verbose and vague, use examples?
The most basic settings influencing the spacing are @code{indent} and
@code{linewidth}.  They are set in the @code{\layout} block.  They
control the indentation of the first line of music, and the lengths of
the lines.

If @code{raggedright} is set to true in the @code{\layout} block, then
the lines are justified at their natural length.  This is useful for
short fragments, and for checking how tight the natural spacing is.

@cindex page layout
@cindex vertical spacing

The option @code{raggedlast} is similar to @code{raggedright}, but
only affects the last line of the piece.  No restrictions are put on
that line.  The result is similar to formatting text paragraphs.  In a
paragraph, the last line simply takes its natural length.
@c Note that for text there are several options for the last line.
@c While Knuth TeX uses natural length, lead typesetters use the same
@c stretch as the previous line.  eTeX uses \lastlinefit to
@c interpolate between both these solutions.

@node Line breaking
@subsection Line breaking

@cindex line breaks
@cindex breaking lines

Line breaks are normally computed automatically.  They are chosen so
that lines look neither cramped nor loose, and that consecutive lines
have similar density.

Occasionally you might want to override the automatic breaks; you can
do this by specifying @code{\break}.  This will force a line break at
this point.  Line breaks can only occur at places where there are bar
lines.  If you want to have a line break where there is no bar line,
you can force an invisible bar line by entering @code{\bar
""}.  Similarly, @code{\noBreak} forbids a line break at a 
point.


@cindex regular line breaks
@cindex four bar music. 

For line breaks at regular intervals use @code{\break} separated by
skips and repeated with @code{\repeat}:
@example
<< \repeat unfold 7 @{
         s1 \noBreak s1 \noBreak
         s1 \noBreak s1 \break @}
   @emph{the real music}
>> 
@end example

@noindent
This makes the following 28 measures (assuming 4/4 time) be broken every
4 measures, and only there.

@refcommands

@code{\break}, and @code{\noBreak}.
@cindex @code{\break}
@cindex @code{\noBreak}

@seealso

Internals: @internalsref{BreakEvent}.


@node Page breaking
@subsection Page breaking

The default page breaking may be overriden by inserting
@code{\pageBreak} or @code{\noPageBreak} commands.  These commands are
analogous to @code{\break} and @code{\noBreak}.  They should be
inserted at a bar line.  These commands force and forbid a page-break
from happening.  Of course, the @code{\pageBreak} command also forces
a line break.

Page breaks are computed by the @code{page-breaking} function in the
@code{\paper} block. 

To force a new page for a new piece (in a collection of pieces or a
piece in several movements), use @code{breakbefore} in the header.

@example
\header@{
  breakbefore = ##t
@}
@end example

@refcommands

@cindex @code{\pageBreak}
@code{\pageBreak}
@cindex @code{\noPageBreak} 
@code{\noPageBreak} 


@node Multiple movements
@subsection Multiple movements

@cindex bibliographic information
@cindex titles
@cindex composer
@cindex Music engraiving by LilyPond

A document may contain multiple pieces of music and texts.  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

@cindex @code{\book}

The movements and texts are combined together in a @code{\book} block,
like

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


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.

@cindex Engraved by LilyPond
@cindex signature line

@example 
\book @{
  \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


@node Creating titles
@subsection Creating titles

Titles are created for each @code{\score} block, and over a
@code{\book}.

The contents of the titles are taken from the @code{\header} blocks.
The header block for a book supports the following
@table @code
@item dedication
The dedicatee of the music, centered at the top of the first page.

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

@item subtitle
Subtitle, centered below the title.

@item subsubtitle
Subsubtitle, centered below the subtitle.

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

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

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

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

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

@item instrument
Name of the instrument, centered below the arranger.

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

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

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

@lilypond[quote,verbatim,linewidth=11.0\cm]
\paper {
  linewidth = 9.0\cm
  vsize = 10.0\cm
}

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

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

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
@item bookTitleMarkup
  This is the title put over an entire @code{\book} block.  Typically,
  it has the composer and the title of the piece
  
@item scoreTitleMarkup
  This is the title put over a @code{\score} block within a
@code{\book}.  Typically, it has the name of the movement (@code{piece}
field).

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

  @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.

@item oddFooterMarkup
  This is the page footer for odd-numbered pages. 
  
@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 Sound output
@section Sound 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.

@refbugs

Many musically interesting effects, such as swing, articulation,
slurring, etc., are not translated to midi.

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.

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

@menu
* Creating MIDI files::         
* MIDI block::                  
* MIDI instrument names::       
@end menu

@node Creating MIDI files
@subsection Creating MIDI files 

To create a MIDI from a music piece of music, add a @code{\midi} block
to a score, for example,

@example 
\score @{
  @var{...music...}
  \midi @{ \tempo 4=72 @}
@}
@end example 

The tempo is specified using the @code{\tempo} command.  In this
example the tempo of quarter notes is set to 72 beats per minute.


If there is a @code{\midi} command in a @code{\score}, only MIDI will
be produced.  When notation is needed too, a @code{\layout} block must
be added

@example 
\score @{
  @var{...music...}
  \midi @{ \tempo 4=72 @}
  \layout @{ @}
@}
@end example 
@cindex layout block



Ties, dynamics, and tempo changes are interpreted.  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 fractions can be adjusted by
@code{dynamicAbsoluteVolumeFunction} in @internalsref{Voice} context.
For each type of MIDI instrument, a volume range can be defined.  This
gives a basic equalizer control, which can enhance the quality of
the MIDI output remarkably.  The equalizer can be controlled by
setting @code{instrumentEqualizer}.


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


The MIDI block is analogous to the layout block, but it is somewhat
simpler.  The @code{\midi} block can contain
@cindex MIDI block

@itemize @bullet
  @item a @code{\tempo} definition, and
  @item context definitions.
@end itemize

A number followed by a period is interpreted as a real number, so
for setting the tempo for dotted notes, an extra space should be
inserted, for example

@example
\midi @{ \tempo 4 . = 120 @} 
@end example


@cindex context definition

Context definitions follow precisely the same syntax as within the
\layout block.  Translation modules for sound are called performers.
The contexts for MIDI output are defined in @file{ly/@/performer@/-init@/.ly}.


@node MIDI instrument names
@subsection MIDI instrument names

@cindex instrument names
@cindex @code{Staff.midiInstrument}

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

@example
\set Staff.midiInstrument = "glockenspiel"
@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.