[lilypond.git] / Documentation / tex / refman.yo

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COMMENT( This document contains Mudela fragments.  You need at least
Yodl-1.30.18 to convert this to tex or html.

TODO

in stead <-> instead
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article(Mudela Reference Manual)
      (Adrian Moriano, Han-Wen Nienhuys and Jan Nieuwenhuizen)
      (nop()PIPETHROUGH(date "+%B %d, %Y")()()nop())

COMMENT(

* The [ ] look weird

* paragraphs have too much space.

)


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bf(This document is not up to date).  All rendered examples of course
are current, but the rest probably isn't.  Adjusting the tutorial was
considered more important than writing the reference manual.  We
apologize for the inconvenience.  For a complete and up-to-date
definition, see file(lily/parser.yy), file(lily/lexer.ll), and the
init files.

This document describes the the GNU LilyPond input format, which is an
effective language for defining music.  We call this language (rather
arrogantly) The Musical Definition Language or Mudela, for
short.footnote(If anybody comes up with a better name, we'd gladly
  take this. Gourlay already uses Musical Description Language,
  G-Sharp Score Definition Language.  ISO standard 10743 defines a
  Standard Music Description Language.  We're not being original here.)

The first aim of Mudela is to define a piece of music, being complete
from both from a musical typesetting, as from a musical performing
point of view.

The Musical Definition Language (Mudela), has a logical structure,
making use of identifiers, that allows for flexible input, and
definition reuse. See the documentation file file(MANIFESTO), included
with the LilyPond sources for reasons and design considerations.


sect(Running LilyPond)

When invoked with a filename that has no extension, LilyPond will try adding
a file(.fly) extension first, and a file(.ly) extension second.  
If the filename ends with 
file(.fly),  LilyPond processes  the file as music using
file(init.fly).  In this case, LilyPond does something
like:
verb(\score {
  \notes\relative c {
    \input "yourfile.fly"
  }
  \paper{}
  \midi{}
})
If you invoke LilyPond with a file file(foo.)var(ext) that doesn't
have the file(.ly) extension then LilyPond will look for a file called
file(init.)var(ext) and process this file.  The file
file(init.)var(ext) must contain the code(\maininput) keyword or LilyPond
will not read the user specified file.


sect(Syntax)

subsect(Basic Mudela)

A Mudela file consists of keywords with arguments and identifier
assignments separated by spaces, tabs or newlines.  (Semicolons are
used by some keywords but are not generally required.)  A one line
comment is introduced by a code(%) character.  Block comments are
started by code(%{) and ended by code(%}).  They cannot be nested.

Mudela supports several types:

description(

dit(integer) 
Formed from an optional minus sign followed by digits.  Arithmetic
operations cannot be done with integers, and integers cannot be mixed
with reals.

dit(real) 
Formed from an optional minus sign and a sequence of digits followed
by a emph(required) decimal point and an optional exponent such as
code(-1.2e3).  Reals can be built up using the usual operations:
code(+), code(-), code(*), and code(/), with parentheses for grouping.

dit(string) 
Begins and ends with the code(") character.  To include a code(")
character in a string write code(\").  Various other backslash
sequences have special interpretations as in the C language.  A string
that contains no spaces can be written without the quotes.  See
Section ref(modes) for details on unquoted strings; their
interpretation varies depending on the situation.  On the right side
of identifier assignments and within the code(\header) keyword,
strings can be concatenated using the code(+) character.

dit(dimension) Consists of a real followed by one of the dimension
keywords: code(\mm), code(\pt), code(\in), or code(\cm).  Dimensions
are converted immediately to a real which gives the dimension in
points, so they can be mixed with reals, but the result is no longer
of type dimension.  The keywords that require a dimension
(code(\shape) and code(\symboltables)) will not accept this.

dit(pitch) 
A pitch is a string which is the name of a pitch.  Example: code(a).
The pitch names can be redefined with the code(\notenames) keyword.
See Section(notelang) for pitch names in different languages.  Pitches
can only be specified inside note mode which is specified with
code(\notes).  Therefore, keywords which require pitch arguments must
appear inside code(\notes).  

dit(music) 
Music is a compound type: arbitrarily complicated expressions with a
hierarchical structure can be formed from simple building blocks.  The
simplest expression of type music is a single note.  A note is formed
from a pitch and an optional duration and must be specified within
code(\notes).  See Section ref(notedesc) for details.  More
complicated expressions of type music are formed by surrounding a
sequence of expressions of type music with braces code({) and code(})
or with angle brackets code(<) and code(>).  Items appearing in braces
will be treated as serial. Items in angle brackets will be
simultaneous.  So for example code({ c e g }) represents an arpeggio
and code(< c e g >) represents a chord.  These items can be nested any
way you like.  This simple example shows how three chords can be
expressed in two different ways:
mudela(fragment,verbatim,center)(
\notes<{a b  c'}{c' d' e'}{e' f' g'}>
\notes{<a c' e'><b  d' f'><c' e' g'>}
)

)


COMMENT(
Compound types are built up from the simple types.  The compound types
are: arglist, assignlist and musiclist.  An arglist is a
white space separated list of integers, reals and or strings surrounded
by braces code({) and code(}).  An assignlist is a list of 
identifier assignments, which have the form var(key)code(=)var(value).
A statement in Mudela has one of three forms:
verb(\keyword argument
\keyword argument1 argument2 ... ;
string=value)
)

subsect(Identifiers)

Identifiers allow names to be assigned to constants, music, or other
Mudela structures.  To assign an identifier you use
var(name)=var(value) and to refer to an identifier, you preceed its
name with a backslash: code(\)var(name).  It is legal to redefine an
identifier in terms of its old value: code(foo = \foo * 2.0).
Identifier assignments must appear at the top level in the Mudela
file.

An identifier can be created with any string for its name, but you
will only be able to refer to identifiers whose names begin with a
letter and are entirely alphanumeric.  It is also impossible to refer
to an identifier whose name is the same as the name of a keyword.  The
following words are keywords:
verb(absdynamic   header         musicalpitch   score         transpose
accepts      in             notenames      script        type     
bar          include        notes          shape         version  
cadenza      key            output         skip        
clef         keysignature   paper          spandynamic 
cm           lyric          partial        symboltables
consists     maininput      penalty        table       
duration     mark           property       tempo       
font         midi           pt             time        
grouping     mm             relative       translator)

The right hand side of an identifier assignment is parsed completely
when the assignment is made.  It therefore must have any context
specified in the definition.  For example, you must write
code(foo=\notes{a8 b c}) rather than code(foo={a8 b c}).  Even though
the context is specified in the definition, you must refer to the
identifier inside the correct context:
verb(foo = \paper{ linewidth = 6.0\in }
\score{
  \notes{ ... }
  \paper{ \foo }
})
If code(\foo) is used here without the surrounding code(\paper) then
an error will result.

Identifiers can be set equal to integers, reals, strings, music,
durations (specified with code(\duration)), note ornaments (specified
with code(\script), dynamics commands, or code(:)), translator
definitions, the code(\paper) block, the code(\midi) block or the
code(\score) block.  When identifiers are used for translators, the
code(\paper), code(\midi), and code(\score) blocks, they may only be
referred to as the first item in a block.  So code(\paper{\one \two})
is illegal because the identifier code(\two) is not the first thing in
the block.



COMMENT(
subsect(Hierarchical structures)

The general structure consists of declarations:
verb(IDENTIFIER = \TYPE{
        <type specific data>
})
and instantiations:

verb(\TYPE{ <type specific data> })

(Currently, code(\score) is the only type that can be instantiated
at top level.)

Most instantiations that use an IDENTIFIER are specified as follows:

verb(\TYPE{ \IDENTIFIER [...] })

Some exceptions on this rule have been made to prevent inputting
Mudela becoming tedious
)


subsect(Modes)
label(modes)

To simplify different aspects of music definition (entering the notes
and manipulating them) Mudela has three different input modes which
affect how unquoted strings are interpreted.
In each mode, words are identified on the input.  If code("word") is
encountered, it is treated as a string.  If code(\word) is
encountered it is treated as a keyword or as an identifier.  The
behavior of the modes differs in two ways: different modes treat
unquoted words different, and different modes have different rules for
deciding what is a word.  

description(

dit(Normal mode)
At the start of parsing, Mudela is in normal mode.
In normal mode, a word is an alphabetic character followed by
alphanumeric characters.  If code(word) is encountered on the input it
is treated as a string. 

dit(Note mode) Note mode is introduced by the keyword
code(\notes).  In Note mode, words can only contain alphabetic
characters.  If code(word) is encountered, LilyPond first checks for a
notename of code(word).  If no notename is found, then code(word) is
treated as a string.  If you mistype a notename, the parser will most
likely complain that you should be in code(\lyric) mode to do lyrics. 

dit(Lyric mode) Lyrics mode is introduced by the keyword
code(\lyric).  This mode is has rules that make it easy to include
punctuation and diacritical marks in words.  A word in Lyrics mode
begins with: an alphabetic character, code(_),
code(?), code(!), code(:), code('), 
the control characters code(^A) through code(^F), code(^Q) through
code(^W), code(^Y), code(^^), any 8-bit character with ASCII code over
127, or a two character combination of a backslash followed by one
of code(`), code('), code(") or code(^).  
Subsequent characters of a word can be any character that is not a
digit and not white space.  One important consequence of this is that
a word can end with code(}), which may be confusing if you thought the
code(}) was going to terminate lyrics mode.  Any code(_) characters
which appear in an unquoted word are converted to spaces, providing a
mechanism for introducing spaces into words without using quotes.  
Quoted words can also be used in lyrics mode to specify words that
cannot be specified with the above rules.  Here are some examples.
Not all of these words are printable by TeX().  
verb(a&@&@&TSI|{[    % a word
\'afoo}         % a word
1THtrhortho     % not a word because it starts with a digit
``Hello''       % not a word because it starts with `
Leise DOEXPAND(Fl\)DOEXPAND("u\)ss{}teren meine Sapfe       % 4 words
_ _ _ _         % 4 words, each one a space
))


COMMENT(
These modes are of a lexical nature. Normal and Note mode largely
resemble each other, save the possibility of entering Reals, 
meaning of code(_) and the resolution of words

What's this about reals?  When can you enter them or not enter them?)


sect(Note Description)
label(notedesc)

subsect(Basic Note Specification)

A note specification has the form 
var(pitch)[var(octavespec)][code(!)][var(duration)].
The pitch of the note is specified by the note's name.  

LilyPond has predefined note names for various languages.  The default
names are the Dutch note names.  The notes are specified by the
letters code(c) through code(b), where code(c) is an octave below
middle C and the letters span the ocatave above that C.  
In Dutch, a sharp is formed by adding
code(-is) to the end of a pitch name.  A flat is formed by adding code(-es).
Double sharps and double flats are obtained by adding code(-isis) or
code(-eses).  
Lily has predefined sets of notenames
for various nop(languages).  See Section ref(notelang) for details.
Rests are specified with the note name code(r) or code(R).  
There is also a note name code(s) which produces a nonprinting note of the
specified duration.

The optional octave specification takes the form of a series of single
quote 
code(') characters or a series of comma code(,) characters.  Each
code(') raises the pitch by one octave; each code(,) lowers the pitch
by an octave.  

mudela(fragment,verbatim,center)(
c' d' e' f' g' a' b' c''
)

mudela(fragment,verbatim,center)(
cis' dis' eis' fis' gis' ais' bis'
)

mudela(fragment,verbatim,center)(
ces' des' es' fes' ges' as' bes'
)

mudela(fragment,verbatim,center)(
cisis' eisis' gisis' aisis' beses'
)

mudela(fragment,verbatim,center)(
ceses' eses' geses' ases' beses'
)

Whenever a C-sharp is desired,  you must specify a C-sharp.  LilyPond
will determine what accidentals to  typeset  depending on the  key and
context.   
A reminder accidental can be forced by
using the  optional exclamation mark `code(!)'
on a pitch.
mudela(fragment,verbatim,center)(
cis' d' e' cis'  c'! d' e' c' 
)


Durations are entered as their reciprocal values
mudela(fragment,verbatim,center)(
a'1 a'2 a'4 a a'8 a a'16 a'32 a'64
)
mudela(fragment,verbatim,center)(
r1 r2 r4 r8 r16 r32
)

If the duration is omitted then it is set equal to the previous
duration.  If there is no previous duration, then a quarter note is
assumed.  
The duration can be followed by a dot code(.) to obtain dotted note
lengths.  
mudela(fragment,verbatim,center)(
a'4. b'4.
)

In addition, the duration can be followed by a multiplier which is
introduced with the asterisk code(*) and can be an integer or a
fraction.  The multiplier changes the duration that LilyPond uses
internally for the note, but for notes it 
does not change the symbol that is printed.  
mudela(fragment,verbatim,center)(
c'4*2 c'4*2 d'8*2/3 d'8*2/3
)
For long rests with durations equal to an integer number of whole notes,
LilyPond produces output that indicates the duration of the rest.  If you use
code(r) then one rest symbol will be printed and several measures left blank.
If you use code(R) then all of the measure will be filled with whole rests.
If you set the code(Score.SkipBars) property, then only one measure will be
printed; with code(R), a number indicating the length of the rest will be
displayed.  
mudela(fragment,verbatim,center)(
r1*3 R1*3
\property Score.SkipBars=1
r1*3 R1*3)

Extra long notes can be obtained using the code(\breve) and
code(longa) durations:
mudela(fragment,verbatim,center)(
c'\breve gis'\longa
)


subsect(Note Spanners: Beams, Tuplets, Slurs and Ties)

A beam is specified by surrounding the beamed notes with brackets
code([) and code(]).  
mudela(fragment,verbatim,center)(
[a'8 a'] [a'16 a' a' a']
)

In order to create triplets, you must use a length multiplier after
the brackets.  An open bracket code([) followed by a fraction
instructs LilyPond to print a number over the beam, and it also
starts multiplying all note lengths by the fraction.  The closing
bracket code(]) should be followed by the fraction code(1/1) in order
to restore normal note lengths.  To create a triplet without a beam,
place a backslace code(\) before the opening and closing brackets. 

For example, in an ordinary triplet, the notes have duration 2/3 as
long as normal. 
mudela(fragment,verbatim,center)(
[2/3 a'8 a' a' ]1/1 \[2/3 b'4 b' b'\]1/1
)

There is a shorthand that can be used when you 
want notes lengths multiplied by 2/n.  
The 2 can be omitted after the open bracket
and the first 1 can be omitted after the closing bracket.  
mudela(fragment,verbatim,center)(
[/3 b'8 b' b' ]/1  \[/3 a'4 a'8\]/1
)

COMMENT(This next bit needs to be fixed...or the language needs to be
fixed.)

Here is a combination
mudela(fragment,verbatim,center)(
[/3 a'8 a'16 a'] a'8 \]
)

Another type of spanner is the slur.  Slurs connects chords and try to
avoid crossing stems.  A slur is started with code(CHAR(40)) and stopped with
code(CHAR(41)).  The starting code(CHAR(40)) appears to the right of the first note
in the slur.  The terminal code(CHAR(41)) apppears to the left of the first
note in the slur.  This makes it possible to put a note in slurs from
both sides:
mudela(fragment,verbatim,center)(
f'()g'()a' [a'8 b']( a'4 g' )f'
)

A tie connects two adjacent note heads.  When used with chords, it
connects all of the note heads.  Ties are indicated using the tilde symbol
code(~) by analogy with TeX()'s tie which connects words.  For ties
between chords, the input convention is somewhat peculiar.  You cannot
write code(<c g>~<c g>), but rather must put the tilde after
a note within the first chord.  

mudela(fragment,verbatim,center)(
e' ~ e' <c'~ e' g'><c' e' g'>
)


subsect(Note Ornaments)

A variety of symbols can appear above and below notes to indicate
different characteristics of the performance.  
These symbols can be
added to a note with `var(note)code(-\)var(name)'.  Numerous different
symbols are defined in file(script.ly).  Each symbol is defined using
the code(\script) keyword which specifies where symbols appear.
Symbols can be forced to appear above the note by writing
`var(note)code(^\)var(name)', and they can be forced to appear below
by writing `var(note)code(_\)var(name)'.  Here is a chart showing
symbols above notes, with the name of the corresponding symbol
appearing underneath.  

mudela()(
\score{
 < \notes{ c''-\accent c''-\marcato c''-\staccatissimo f'-\fermata 
          c''-\stopped c''-\staccato c''-\tenuto c''-\upbow c''-\downbow
          c''-\lheel c''-\rheel  c''-\ltoe  c''-\rtoe  c''-\turn
          c''-\open  c''-\flageolet  c''-\reverseturn 
          c''-\trill
          c''-\prall c''-\mordent c''-\prallprall  c''-\prallmordent
          c''-\upprall c''-\downprall }
  \type Lyrics \lyric{  
        accent      marcato      staccatissimo fermata stopped
           staccato tenuto upbow downbow lheel rheel ltoe rtoe  turn
           open  flageolet reverseturn 
             trill  prall
           mordent prallprall prallmordent uprall  downprall }>
  \paper{linewidth  = 5.875\in
         indent = 0.0
        }
}
)

COMMENT( The following are defined in script.ly but do not work:

portato lbheel rbheel lbtoe rbtoe lfheel rfheel lftoe rftoe )

In addition, it is possible to place arbitrary strings of text or
TeX() above or below notes by using a string instead of an identifier:
`code(c^"text")'.  Fingerings can be placed by simply using digits.
All of these note ornaments appear in the printed output but have no
effect on the MIDI rendering of the music.

To save typing,  a few common symbols  can  be  abbreviated  with
single characters:
mudela()(
\score{ \notes {
        \property Voice.textstyle = typewriter
        c''4-._"c-." s4
        c''4--_"c-{}-"  s4
        c''4-+_"c-+" s4
        c''4-|_"c-|" s4
        c''4->_"c->"  s4
        c''4-^_"c-\\^{ }"  s4 }
        \paper { linewidth = 12.\cm; }})

Dynamic marks are specified by using an identifier after a note
without a dash: code(c4 \ff).  Note that this syntax is inconsistent
with the syntax for other types of ornaments.  The available dynamic
marks are: code(\ppp), code(\pp), code(\p), code(\mp), code(\mf),
code(\f), code(\ff), code(\fff), code(\fp), code(sf), and code(\sfz).

A crescendo mark is started with code(\cr) and terminated with
code(\rc).  A decrescendo mark is started with code(\decr) and
terminated with code(\rced).

Tremolo marks can be printed by a note by adding code(:)[var(length)]
after the note.  The length must be at least 8.  A var(length) value
of 8 gives one line across the note stem.  
If the length is omitted,
then the last value is used, or the value of the code(Abbrev)
property if there was no last value.  To place tremolo marks in
between two notes, begin with code([:)var(length) and end with code(]).
The tremolo marks will appear instead of beams.  Putting more than two
notes in such a construction will produce odd effects. 
mudela(fragment,verbatim,center)(
c'2:8 c':32 [:16 e'1 g'] [:8 e'4 f']
)

COMMENT(
Is the last paragraph correct?  Is it called "tremolo"?  Why is
"abbreviation" used?  (What is the unabreviated form?)


mudela(fragment,verbatim,center)(
c'4:32 [:16 c'8 d'8]
)

)


sect(Other Ways to Enter Pitches)

subsect(Pitch Names in Other Languages)
label(notelang)

The pitch names can be easily redefined using the code(\notenames) command.
Note name definitions have been provided in various languages.  
Simply include the language specific init file.  For example:
code(\include "english.ly").  The available language files and the names
they define are:

verb(                        Note Names               sharp       flat
nederlands.ly  c   d   e   f   g   a   bes b   -is         -es
english.ly     c   d   e   f   g   a   bf  b   -s/-sharp   -f/-flat
deutsch.ly     c   d   e   f   g   a   b   h   -is         -es
norsk.ly       c   d   e   f   g   a   b   h   -iss/-is    -ess/-es
svenska.ly     c   d   e   f   g   a   b   h   -iss        -ess
italiano.ly    do  re  mi  fa  sol la  sid si  -d          -b)

subsect(Relative Pitch Specification)
label(relative)

One very common error when entering music is to place notes in the wrong
octave.  One way to avoid being confused by large numbers of octave changing
marks is to use
the code(\relative) keyword. 
Music which appears within code(\relative) is
interpreted differently.  The octave of a note is determined by making it as
close to the previous note as possible.  The octave changing marks code(') and
code(,) can then be added to raise or lower this note by octaves.  You have to
specify a starting pitch because the first note of a list has no predecessor.  

mudela(fragment,verbatim,center)(
\relative c'' { c d b c, d b c' d 
                b c,, d b }
)

When the preceeding item is a chord, the first note of the chord is used to
determine the first note of the next chord.  But other notes within the second
chord are determined by looking at the immediately preceeding note.  

mudela(fragment,verbatim,center)(
\relative c' { <c e g> 
    <c' e g> <c, e' g> }
) 

The code(\relative) keyword can only appear in music, so there must be a
surrounding code(\notes) keyword which does not appear in the fragments shown
above.  Also note that if the music passed to a code(\relative) keyword 
contains a code(\transpose) keyword, the tranposed music will not be
processed in relative mode.  An additional code(\relative) must be placed
inside the code(\transpose).  


subsect(Tranposition of Pitches)
label(transpose)

Another way to modify the meaning of the note names is to use the
code(\transpose) keyword.  This keyword allows you to transpose music.
To use transposition, specify the pitch that middle C should be tranposed to.
It is important to distinguish between enharmonic pitches as they can produce
different transpositions.  To transpose up half a step, for example, either 
code(\transpose cis') or code(\transpose des') will work.  But the first
version will print sharps and the second version will print flats.  
In this example, a scale in the key of E is transposed to F, or to E-sharp 
with odd results.
mudela(fragment,verbatim,center)(
\relative c' { \key e; 
  e fis gis a b cis dis e }
)
mudela(fragment,verbatim,center)(
\transpose des' \relative c' { \key e; 
   e fis gis a b cis dis e }
)
mudela(fragment,verbatim,center)(
\transpose cis' \relative c' { \key e; 
    e fis gis a b cis dis e }
)
If you want to use both code(\transpose) and code(\relative), then you must use
code(\transpose) first.  Any code(\relative) keywords that are outside the 
code(\transpose) have no effect on notes that appear inside the
code(\transpose).  

sect(Lyrics)

Lyrics are entered like notes, with pitches replaced
by text.  For example code(Twin-4 kle4 twin-4 kle4) enters four
syllables, each with quarter note duration.  Note that the hyphen has
no special meaning for lyrics, and does not introduce special symbols.
See Section ref(modes) for a description of what is interpreted as a lyric.

In order to instruct LilyPond to write lyrics underneath the
staff, you must enter the lyrics context with code(\type Lyrics).  
Lyrics should be entered in lyrics mode which is entered with code(\lyric).

Spaces can be introduced into a lyric either by using quotes (code("))
or by using an underscore without quotes: code(He_could4 not4).  All
unquoted underscores are converted to spaces.  Here is a full example: 
mudela(verbatim)(\score{
  <  \notes \transpose c'' {c d e c | c d e c | e f g'2 | 
                              e'4 f g'2 \bar "|."; }
     \type Lyrics \lyric { 
              DOEXPAND(Fr\)`e-4 re Ja- que DOEXPAND(Fr\)`e- re Ja- que
              Dor- mez vous?2 Dor-4 mez vous?2  }
  >
})

COMMENT(
URG
                        Fr\`e-4 re Ja- que
                        Fr\`e- re Ja- que
Why does this warrant an URG?
)


COMMENT(

sect(Chords and Voices)

Here's a simple chord
mudela(fragment,verbatim,center)(
<c e g>
)

here are a few
mudela(fragment,verbatim,center)(
<
        { c'()d'()c' }
        { e'()f'()e' }
        { g'()a'()g' }
>
)

and similarly voices
mudela(fragment,verbatim)(
<
        { \voiceone c'4 g' c' g' }
        { \voicetwo c2 g2 }
>
)

)

sect(Time)  

LilyPond aligns all musical objects according to the amount of time
they occupy.  All of these objects have a duration.  When music is
written sequentially using braces the duration is the sum of the 
durations of the elements.  When music is stacked into simultaneous music 
using angle
brackets, the duration is the maximum of the durations of the
elements.  

Because LilyPond knows the durations of all musical elements, the time
signature enables LilyPond to draw bar lines automatically.  The time
signature is specified with the code(\time) keyword: code(\time 3/4).
If no time signature is given, LilyPond assumes 4/4.  The automatic
generation of bar lines can toggled with the code(\cadenza) keyword,
and an incomplete measure at the start of the music can be created
using the code(\partial) keyword: code(\partial 8*2;) creates a
starting measure lasting two eighth notes.

In order to help with error checking, you can insert bar markers in
your music by typing code(|).  Whenever LilyPond encounters a code(|)
that doesn't fall at a measure boundary, she prints a warning message.

Rhythmic grouping is  a concept closely associated with this. 
A default grouping is selected for the chosen time signature.  
The default consists of combinations of 2 and 3 beats with as many
groups of 3 as possible, and the groups of 3 coming first.  For
example, 4/4 is divided into 2+2 and 8/8 is divided into 3+3+2.  This
default grouping can be changed using the \grouping keyword which
takes a list of durations to specify the grouping. 


COMMENT(
sect(Composition: forming bigger structures)
label(sec:grammar)

The computer savy user may be interested in a more formal
specification.  We can capture what have learned about forming
sentences in Mudela in a context-free grammar.

latexcommand(\smallskip)

table(2)(lll)(
        row(cell(em(Music))cell(: em(Note)))
        row(cell()cell(code(|) em(Rest)))
        row(cell()cell(code(|) code({) em(MusicList) code(})))
        row(cell()cell(code(|) code(<) em(MusicList) code(>)))
        row(cell()cell(code(|) em(Command)))
        row(cell()cell(code(|) code(\type) em(string) code(=) em(string)  em(Music)))
        row(cell()cell(;))
        row(cell(em(MusicList))cell(: em(empty)))
        row(cell()cell(code(|)  em(MusicList)  em(Music)))
        row(cell()cell(;))
)

latexcommand(\smallskip)

In mathematics you can form expressions by combining expressions,
which are ultimately some kind of atom or terminal symbol.  The same
goes for Mudela: there are some basic building blocks, and by
combining those you create complex music.

You can combine music in three ways:
itemize(
it()If you enclose a sequence of music-elements in braces ( code({)
    and code(}) ), then you form another kind of music called
sequential music
    with those pieces.
  The duration of sequential composition is the sum of the durations of its elements
  verb(
      { c c g g a a g2 }      % twinkle twinkle
      { { c c g g} { a a g2 } }
  )
it()You can stack music by enclosing a sequence of music elements
    with code(<) and code(>). This is called simultaneous music.  
    The duration of a simultaneous composition is the maximum of the durations 
    of its elements Example:
    verb(
        <a4 {cis8 cis8} e'4>      % a-major chord
    )
it()You can form music by transposing music:
    verb(
    \transpose  
        d       % from c to the d that's almost one octave down
                { e4 f4 }       % the horizontal music
)
it()verb(\type)
it()verb(\property)
it()verb(\translator)
it()verb(\relative)
)

Of course you can also combine these three mechanisms.
verb(
{ c <c e> <c e g> <c e g \transpose d' dis > }  % 4 increasing chords
)

)


sect(Keywords)

Keywords sometimes appear alone, but usually they require arguments.
A keyword may have a single argument, a sequence of arguments in
braces, or a sequence of arguments separated by spaces and terminated
by a semicolon.  The precise syntax of each keyword is shown below.
Keywords must appear in the right context.  If you use a keyword in
the wrong place, even if the usage is syntactically correct, you will
get the message ``parse error'' from LilyPond.


description(

dit(code(\absdynamic) code({) var(code) code(})) Internal keyword for
printing dynamic marks such as $f$ under music.  The parameter
var(code) is unsigned and specifies the dynamic mark to print.
Normally you should use the more user friendly abbreviations defined
in the init file file(dynamic.ly).

dit(code(\accepts) var(string)code(;)) This keyword can appear only within a
code(\translator) block.  It specifies what contexts are allowed with the
context that is being defined.  See Section ref(translators).  

dit(code(\bar) var(bartype)code(;)) Prints a special bar symbol, or at
measure boundaries, replaces the regular bar symbol with a special
symbol.  The argument var(bartype) is a string which specifies the
kind of bar to print.  Options are code(":|"), code("|:"),
code(":|:"), code("||"), code("|."), code(".|"), or code(".|.").
These produce respectively a right repeat, a left repeat, a double
repeat, a double bar, a start bar, an end bar, or a thick double bar.
If var(bartype) is set to code("empty") then nothing is printed, but a
line break is allowed at that spot.  Note that the printing of special bars
has no effect on the MIDI output.

dit(code(\cadenza) var(togglevalue)code(;)) Toggles the automatic generation
of bar lines.  If var(togglevalue) is 0 then bar line generation is
turne off.   If var(togglevalue) is  1  then a bar is  immediately
printed and bar generation is turned  on.

dit(code(\clef) var(clefname)code(;)) Allowed only in music.  
Sets the current clef.  The argument is
a string which specifies the name of the clef.  Several clef names are
supported.  If code(_8) or code(^8) is added to the end of a clef
name then the clef lowered or raised an octave will be generated.  
Here are the supported clef names with middle C shown in each clef:
mudela(center)(
\score{
  \notes{ \cadenza 1;
   %\property Voice.textstyle = typewriter
   \clef subbass; c'4-"\kern-10mm subbass" 
           \clef bass;    c'4^"\kern -8mm bass"
           \clef baritone; c'4_"\kern -10mm baritone"
           \clef varbaritone; c'4^"\kern -10mm varbaritone"
           \clef tenor;     c'4_"\kern -10mm tenor"
           \clef "G_8";   c'4^"\kern -6mm G\_8"  }  
   \paper{ linewidth= 4.5 \in }
}
)
mudela(center)(
\score{
  \notes{\cadenza 1; \clef alto;    c'4_"\kern -10mm alto"
           \clef mezzosoprano; c'4^"\kern -10mm mezzosoprano"
           \clef soprano;  c'4_"\kern -10mm soprano"
           \clef treble;  c'4^"\kern -6mm treble"
           \clef french;  c'4_"\kern -10mm french" }  
  \paper{ linewidth= 4.5 \in }
}
)
The treble  clef  can also  be obtained using  the  names code(G) or
code(violin).  The bass clef is also available by code(\clef  F). 

dit(code(\cm)) Specify a dimension in centimeters. 

dit(code(\consists) var(string)code(;)) This keyword can appear only within a
code(\translator) block.  It specifies that an engraver named
var(string) should be added to the translator.  See Section ref(translators).

dit(code(\duration) code({) var(length) var(dotcount) code(})) Specify note
duration.  The parameter var(length) is the negative logarithm (base
2) of duration: 1 is a half note, 2 is a quarter note, 3 is an eighth
note, etc.  The number of dots  after  the  note is given by
var(dotcount). 

dit(code(\font) var(string)) Internal keyword.  Used within
code(\symboltables) to specify the font.

dit(code(\grouping) var(durationseq); )  Sets  the  metric structure of
the measure.  Each argument specifies the duration of one metric unit.
For example, code(\duration 16*5;) specifies a grouping of five beats
together in 5/16 time.  The default grouping is to have as many groups
of 3 as possible followed by groups of two.  

dit(code(\header) code({) var(key1) = var(val1); var(key2) = var(val2); ... code(}))
Specifies information about the music.  A header should appear at the
top of the file describing the file's contents.  If a file has
multiple code(\score) blocks, then a header should appear in
each score block describing its contents.  Tools like code(ly2dvi) can
use this information for generating titles.   Some possible key values
are: title, opus, description, composer, enteredby, and copyright.

dit(code(\in)) Specify a dimension in inches.  

dit(code(\include) var(file)) Include the specified file.  The
argument var(file) is a string.  The full filename including the
file(.ly) extension must be given. 

dit(code(\key) var(pitch)) Change key signature to that of
var(pitch)-major.

dit(code(\keysignature) var(pitchseq);)
Specify an arbitrary key signature.  The pitches from var(pitch) will
be printed in the key signature in the order that they appear on the list.

dit(code(\lyric) var(lyriclist)) Parse var(lyriclist) in lyrics mode.

dit(code(\maininput)) Internal command.  This command is used for creating init
files like file(init.fly) that read the user file into the middle of another
file.  Using it in a user file will lead to an infinite loop.
        
dit(code(\mark) var(unsigned) or code(\mark) var(string)) Allowed in
music only.  Prints a mark over or under (?) the staff.  You must add
code(Mark_engraver) to the Score context and it only seems to work if the
mark appears at the beginning of a line.  

dit(code(\midi) var(statementlist)) Appears in a score block to
indicate that musical output should be produced.  See code(\tempo).

dit(code(\mm)) Specify a dimension in millimeters. 

dit(code(\musicalpitch) code({) var(octave) var(note) var(shift) code(})) 
Specify note pitch.  The octave is specified by an integer,
zero for the octave containing middle C.  The note is a number from 0
to 7, with 0 corresponding to C and 7 corresponding to B.  The shift
is zero for a natural, negative to add flats, or positive to add
sharps.

dit(code(\notenames) var(assignmentlist)) Define new note names.  
The argument is a list of definitions of  the form
var(name) = var(pitch),  where var(pitch) is specified with the
code(\musicalpitch) keyword.  

dit(code(\notes) var(music)) Enter note mode and process the
specified music. 

dit(code(\)code(output) var(string)code(;)) Allowed only in
code(\paper) block.  The parameter var(string) specifies an alternate
name for the TeX() output.  A file(.tex) extension will be added to
var(string) to produce the output file name.

dit(code(\paper) var(statmentlist)) 
Appears in a score block to indicate that the music should be printed.
The var(statmentlist) contains statements that change features of the
output.  See Section ref(paper).  

dit(code(\partial) var(duration)) Specify that the first measure of
the music lasts only for the specified duration.

dit(code(\penalty) code(=) var(int)) Allowed only in music.
Discourage or encourage line breaks.  See identifiers code(\break) and
code(\nobreak) in Section ref(ident). 

dit(code(\property) var(contextname)code(.)var(propname) code(=) var(value))
Sets the var(propname) property of the context var(contextname) to the
specified var(value).  All three arguments are strings.

dit(code(\pt)) Specify a dimension in points. 

dit(code(\relative) var(pitch) var(music)) Processes the specified
var(music) in relative pitch
mode.  In this mode, the octave of a pitch is chosen so that the
pitch is closest to the preceeding pitch.  
The argument var(pitch) is
the starting pitch for this comparision.  In the case of chords, the
first note of a chord is used as the base for the first pitches in the next
chord.  See Section ref(relative).

dit(code(\score) var(statementlist)) Create a Score context.  This
is the top level notation context.  
COMMENT(this still needs work)

dit(code(\script) code({) var(name) var(instaff) var(withstem)
var(location) var(invertible) var(priority) code(})) This keyword is
used the initialization file(script.ly) to define the various symbols
that can appear above and below notes.  The first argument is the name
of the symbol.  The second argument var(instaff) is 1 if the symbol
follows the notehead into the staff and 0 if the symbol stays above or
below the staff lines.  The third parameter var(withstem) is 0 if the
symbol's placement does not depend on the stem direction; it is 1 if
the symbol should be at the stem end of the note and it is -1 if the
symbol should be at the note head end of the note.  The argument
var(location) is set to 1 for symbols that always appear above the
staff; it is -1 for symbols that appear below the staff.  If
var(invertible) is set to 1 then the symbol can be inverted; otherwise
it cannot.  The last argument var(priority) sets a priority for the
order of placement of several symbols on a single note.

dit(code(\shape) code(=) var(indent1) var(width1) var(indent2)
var(width2) ... code(;)) Allowed only within code(\paper).  Each pair
of var(indent) and var(width) values is a dimension specifying how far
to indent and how wide to make the line.  The indentation and width of
successive lines are specified by the successive pairs of dimensions.
The last pair of dimensions will define the characeristics of all
lines beyond those explicitly specified.

COMMENT(First pair of dimensions seems to be skipped.  At least it is
in the example file denneboom.ly.)

dit(code(\skip) var(duration)) Skips the amount of time specified by
var(duration).  A gap will be left for the skipped time with no notes
printed.  It works in Note Mode or Lyrics Mode (but generates a
mysterious error in lyrics).

dit(code(\spandynamic) code({) var(kind) var(toggle) code(})) Internal
keyword for crescendo and decrescendo symbols.  The first parameter
var(kind) is set to 1 for a crescendo and -1 for a decrescendo.  The
second parameter is set to 1 to start the mark and 2 to stop it.
Users should use the abbreviations which are defined in the
initialization file file(dynamic.ly).

dit(code(\symboltables)) Internal keyword.  Used to create symbol
tables.  See initialization files file(paper*.ly), file(feta*.ly), and
file(table*.ly).  

dit(code(\table)) Internal keyword.  Used within code(\symboltables)
to specify the tables.  See initialization files. 

dit(code(\tempo) var(duration) = var(perminute)) Used within
code(\midi) to specify the tempo.  For example, 
`code(\midi { \tempo 4 = 76})' requests output with 76 quarter notes
per minute. 


dit(code(\time) var(numerator)code(/)var(denominator)) Change the time
signature.  The default time signature  is 4/4.  


dit(code(\translator) var(statements) or code(\translator)
var(context) = var(name)) The first variant appears only within
code(\paper) and specifies a translator for
converting music to notation.  The translator is specified with a
single code(\type) statement and a series of code(\accepts), and
code(\consists) statements.  See Section ref(translators). 
The second variant appears in 
music.  It specifies that the current the contexts
contained within the specified context should be shifted to the
context with the specified name.  

COMMENT( \translator seems like a strange name for the second
operation, and is the overloading desireable? )

dit(code(\transpose) var(pitch) var(music)) Transposes the specified
music.  Middle C is tranposed to var(pitch).  This is allowed in music only,
and if it appears inside code(\relative), then any notes specified for
transposition should be specified inside another code(\relative).  See Section
ref(transpose).  

dit(code(\type) var(contexttype) [code(=) var(contextname)]
var(music) or code(\type) var(translatortype)code(;)) The first
variant is used only within music to create an instance of a
context.  The new context can optionally be given a name.  The
specified var(music) is processed in the new context. The second
variant appears within a code(\translator) block and specifies the
type of translator being created.

dit(code(\version) var(string)) Specify the version of Mudela that a
file was written for.  The argument is the version number, for example
code("1.0.1").  Note that the Mudela version is different from the
LilyPond version.

)  


sect(Notation Contexts)

Notation contexts provide information that appears in printed music
but not in the music itself.  A new musical context is created using
the code(\type) keyword: `code(\type) var(contexttype) [code(=)
var(contextname)] var(music)'.  The following context types are
allowed.

description(

dit(code(LyricVoice)) Corresponds to a voice with lyrics.  Handles the printing
of a single line of lyrics.  

dit(code(Voice)) Corresponds to a voice on a staff.
  This context handles the conversion of noteheads,
  dynamic signs, stems, beams, super- and subscripts, slurs, ties and rests.

dit(code(Lyrics)) Typesets lyrics.  It can contain code(LyricVoice) contexts.

dit(code(Staff)) Handles clefs, bar lines, keys,
  accidentals.  It can contain code(Voice) contexts.

dit(code(RhythmicStaff)) A context like code(Staff) but for printing
rhythms.  Pitches are ignored; the notes are printed on one line.  
It can contain code(Voice) contexts. 

dit(code(GrandStaff)) Contains code(Staff) or code(RhythmicStaff)
contexts.  It adds a brace on the left side grouping the staffs
together. The bar lines of the contained staffs are connected vertically.
It can contain code(Staff) contexts.

dit(code(StaffGroup)) Contains code(Staff) or code(RhythmicStaff)
contexsts.  Adds a bracket on the left side, grouping the staffs
together.  The bar lines of the contained staffs are connected vertically.
It can contain code(Staff), code(RhythmicStaff), code(GrandStaff) or code(Lyrics) contexts.  

dit(code(ChoirStaff)) Identical to code(StaffGroup) except that the
contained staffs are not connected vertically.  

dit(code(Score)) This is the top level notation context.  It is specified with
the code(\score) keyword rather than the code(\type) command.  No
other context can contain a code(Score) context.  This context handles
the administration of time signatures.  It also makes sure that items
such as clefs, time signatures, and key-signatures are aligned across
staffs.  It can contain code(Lyrics), code(Staff),
code(RhythmicStaff), code(GrandStaff), code(StaffGroup), and
code(ChoirStaff) contexts.

)

The various contexts have properties associated with them.  These
properties can be changed using the code(\property) command:
`code(\property) var(context)code(.)var(propname) code(=) var(value)'.
Properties can also be set within the code(\translator) block
corresponding to the appropriate context.  In this case, they are
assigned by `var(propname) code(=) var(value)'.  The settings made with
code(\property) are processed after settings made in the code(\translator)
block, so the code(\property) settings will override code(\translator)
settings.  

The code(\property) keyword will create any property you specify.
There is no guarantee that a property will actually be used.  If you
spell a property name wrong, there will be no error message.  In order to find
out what properties are used, you must search the source code 
for code(get_property).  
Properties that are set in one context are inherited by all of the
contained contexts.  This means that a property valid for the Voice
context can be set in the Score context (for example) and thus take
effect in all Voice contexts.  

subsubsubsect(Lyrics properties)

description(

dit(code(textstyle)) Set the font for lyrics.  The available font
choices are code(normaltext), code(roman), code(italic), code(bold)
code(normaltext), code(large), code(Large), code(huge), and
code(finger).  The code(finger) font can only display numbers.  Note
also that you must be careful when using code(\property) in Lyrics
mode.  Because of the way strings are parsed, either put quotes around
the arguments to code(\property) or be sure to leave a space on both
sides of the dot.

dit(code(textalignment)) Controls alignment of lyrics.  Set to \left
to align the left end of the lyric with the note; set to \right to
align the right end of the lyric with the note.  Set to \center to
align the center of the lyric with the note.  

)

subsubsubsect(Voice properties)

description(  

dit(code(midi_instrument)) Sets  the  instrument for MIDI  output. 

dit(code(transposing)) Tranpose the MIDI output.  Set this property to
the number of half-steps to transpose by.

dit(code(ydirection)) Determines the direction of stems, subscripts,
beams, slurs, and ties.  Set to code(\down) to force them down,
code(\up) to force them up, or code(\free) to let LilyPond decide.
This can be used to distinguish between voices on the same staff.  The
code(\stemdown), code(\stemup), and code(\stemboth) identifiers set
this property.  See also the identifiers code(\voiceone),
code(\voicetwo), code(\voicethree) and code(\voicefour).

dit(code(slurydirection)) Set to code(\free) for free choice of slur
direction, set to code(\up) to force slurs up, set to code(\down) to
force slurs down.  The shorthands code(\slurup), code(\slurdown), and
code(\slurboth) are available.

dit(code(slurdash)) Set to 0 for normal slurs, 1 for dotted slurs, and
a larger value for dashed slurs.  Identifiers code(\slurnormal) and
code(\slurdotted) are predefined to set the first two settings.

dit(code(hshift)) Set to 1 to enable LilyPond to shift notes
horizontally if they collide with other notes.  This is useful when
typesetting many voices on one staff.  The identifier code(\shift) is
defined to enable this.

dit(code(dynamicdir)) Determines location of dynamic marks.  Set to
code(\up) to print marks above the staff; set to code(\down) to print
marks below the staff.

dit(code(textalignment)) Controls alignment of superscripted and
subscripted text.  Set to \left to align the left end of the text with
the note; set to \right to align the right end of the text with the
note.  Set to \center to align the center of the text with the note.

dit(code(textstyle)) Set the text style for superscripts and
subscripts.  See above for list of text styles.

dit(code(fontsize)) Can be used to select smaller font sizes for
music.  The normal font size is 0, and the two smaller sizes are -1
and -2.

dit(code(pletvisibility)) Determines whether tuplets of notes are
labelled.  Setting to 0 shows nothing; setting to 1 shows a number;
setting to 2 shows a number and a bracket if there is no beam; setting
to 3 shows a number, and if there is no beam it adds a bracket;
setting to 4 shows both a number and a bracket unconditionally.  

)

subsubsubsect(Staff properties)

description(
 
dit(code(defaultclef)) Determines the default clef.  See code(\clef)
keyword.

dit(code(nolines)) Sets the number of lines that the staff has.
 
dit(code(barAlways)) If set to 1 a bar line is drawn after each note.

dit(code(defaultBarType)) Sets the default type of bar line.  See
code(\bar) keyword.




dit(code(keyoctaviation)) If set to 1, then keys are the same in all
octaves.  If set to 0 then the key signature for different octaves can
be different and is specified independently: code(\keysignature bes
fis').  The default value is 1.  Can be set to zero with
code(\specialkey) or reset to 1 with code(\normalkey).

dit(code(instrument) and code(instr)) If code(Staff_margin_engraver)
is added to the Staff translator, then the code(instrument) property
is used to label the first line of the staff and the code(instr)
property is used to label subsequent lines.
COMMENT(This prints the instrument name on top of the staff lines.)

dit(code(abbrev)) Set length for tremolo to be used if no length is
explicitly specified.

dit(code(createKeyOnClefChange)) Set to a nonempty string if you want key
signatures to be printed when the clef changes.  Set to the empty string (the
default) if you do not want key signatures printed.


dit(code(timeSignatureStyle)) Changes the default two-digit layout
   for time signatures. The following values are recognized:
   description(
      dit(code(C)): 4/4 and 2/2 are typeset as C and struck C,
      respectively. All other time signatures are written with two digits.
      dit(code(old)): 2/2, 3/2, 3/4, 4/4, 6/4 and 9/4 are typeset with
      old-style mensuration marks. All other time signatures are 
      written with two digits.
      dit(code(1)): All time signatures are typeset with a single
      digit, e.g. 3/2 is written as 3.
      dit(code(C2/2,C4/4, old2/2, old3/2, old3/4, old4/4, old6/4 or
      old9/4)): Tells Lilypond to use a specific symbol as time
      signature, independently of the actual time signature.
   )

The different time signature characters are shown below with
their names:
mudela(fragment,center)(
\relative c'' {
\property Voice.textstyle = typewriter
\property Staff.timeSignatureStyle = "C2/2"
\time 2/2; a2^"C2/2" a2 
\property Staff.timeSignatureStyle = "C4/4"
\time 2/2; a2^"C4/4" a2 
\property Staff.timeSignatureStyle = "old2/2"
\time 2/2; a2^"old2/2" a2 
\property Staff.timeSignatureStyle = "old3/2"
\time 2/2; a2^"old3/2" a2 
\property Staff.timeSignatureStyle = "old4/4"
\time 2/2; a2^"old4/4" a2 
\property Staff.timeSignatureStyle = "old6/4"
\time 2/2; a2^"old6/4" a2 
\property Staff.timeSignatureStyle = "old9/4"
\time 2/2; a2^"old9/4" a2 
}
)

COMMENT( timeSignatureSymbol?  timeSignatureChar? )


)
   


subsubsubsect(GrandStaff properties)

description( 

dit(code(maxVerticalAlign)) Set the maximum vertical distance between
staffs.

dit(code(minVerticalAlign)) Set the minimum vertical distance between
staffs.  

)

subsubsubsect(Score properties)

description(

dit(code(SkipBars)) Set to 1 to skip the empty bars that are produced
by multimeasure notes and rests.  These bars will not appear on the
printed output.  Set to zero (the default) to expand multimeasure
notes and rests into their full length, printing the appropriate
number of empty bars so that synrchonization with other voices is
preserved.  COMMENT(meaning of "skip" here seems to be different from
the meaning used for the keyword \skip.)

dit(code(beamquantisation)) Set to code(\none) for no quantization.
Set to code(\normal) to quantize position and slope.  Set to
code(\traditional) to avoid wedges.  These three settings are
available via code(\beamposfree), code(\beamposnormal), and
code(\beampostraditional).

dit(code(beamslopedamping)) Set to code(\none) for undamped beams.
Set to code(\normal) for damped beams.  Set to code(\infinity) for
beams with zero slope.  The identifiers code(\beamslopeproportional),
code(\beamslopedamped), and code(\beamslopezero) each set the
corresponding value.

)
       

COMMENT(

Mystery properties:

bar-number-engraver.cc:  "barScriptPadding"  vertical space for numbers
mark-engraver.cc:        "markScriptPadding" vertical space for marks
span-bar-engraver.cc:    "singleStaffBracket" do single staffs get a bracket?
bar-column-engraver.cc:  "barColumnPriority"        
bar-number-engraver.cc:  "barNumberBreakPriority"   Control horizontal ordering
mark-engraver.cc:        "markBreakPriority"      of bars, clefs, keysig
staff-margin-engraver.cc:"marginBreakPriority"    etc.  Slated for revision
)

sect(Pre-defined Identifiers)
label(ident)

Various identifiers are defined in the initialization files to
provide shorthands for some settings.  

description(
dit(code(\break)) Force a line break in music by using a large
argument for the keyword code(\penalty). 
dit(code(\center)) Used for setting textalignment property.  Is set to 0.
dit(code(\cr)) Start a crescendo.
dit(code(\decr)) Start a decrescendo.
dit(code(\down)) Used for setting direction setting properties.  Is
equal to -1.  
dit(code(\f)) Print forte symbol on the preceeding note.
dit(code(\ff)) Print fortissimo symbol on the preceeding note. 
dit(code(\fff)) Print fortississimo symbol on preceeding note. 
dit(code(\fp)) Print fortepiano symbol on preceeding note. 
dit(code(\free)) Used for setting direction setting properties.  Is
equal to 0.  
dit(code(\Gourlay)) Used for setting the paper variable
code(castingalgorithm).  Is equal to 1.0.  
dit(code(\infinity)) Used for setting the Score.beamslopedamping
property.  Is actually equal to 10000.  
dit(code(\left)) Used for setting textalignment property.  Is equal to -1.
dit(code(\mf)) Print mezzoforte symbol on preceeding note. 
dit(code(\mp)) Print mezzopiano symbol on preceeding note. 
dit(code(\nobreak)) Prevent a line break in music by using a large
negative argument for the keyword code(\penalty). 
dit(code(\none)) Used for setting Score.beamslopedamping and
Score.beamquantisation properties.  Is equal to 0.
dit(code(\normal)) Used for setting Score.beamslopedamping and
Score.beamquantisation properties.  Is equal to 1.
dit(code(\normalkey)) Select normal key signatures where each octave
has the same key signature.  This sets the Staff.keyoctaviation property.
dit(code(\p)) Print a piano symbol on preceeding note. 
dit(code(\pp)) Print pianissimo symbol on preceeding note. 
dit(code(\ppp)) Print pianississimo symbol on preceeding note. 
dit(code(\rc)) Terminate a crescendo. 
dit(code(\rced)) Terminate a decrescendo
dit(code(\right)) Used for setting textalignment property.  Is set to 1.
dit(code(\sf)) Print a ?? symbol on preceeding note. 
dit(code(\sfz)) Print a ?? symbol on preceeding note. 
dit(code(\shiftoff)) Disable horizontal shifting of note heads that collide.  
Sets the Voice.hshift property.
dit(code(\shifton)) Enable note heads that collide with other note heads
to be shifted horiztonally.  Sets the Voice.hshift property.
dit(code(\slurboth)) Allow slurs to be above or below notes.  This
sets the Voice.slurydirection property. 
dit(code(\slurdown)) Force slurs to be below notes. This sets the
Voice.slurydirection property. 
dit(code(\slurup)) Force slurs to be above notes.  This sets the
Voice.slurydirection property.  
dit(code(\specialkey)) Allow keys signatures do differ in different
octaves.  This sets the Staff.keyoctaviation property.  
dit(code(\stemboth)) Allow stems, beams, and slurs to point either
direction.  This sets the Voice.ydirection property. 
dit(code(\stemdown)) Force stems, beams, and slurs to point down.
This sets the Voice.ydirection property. 
dit(code(\stemup)) Force stems, beams and slurs to point up.  This
sets the Voice.ydirection property. 
dit(code(\traditional)) Used for setting the 
Score.beamquantisation property.  Is equal to 2.  
dit(code(\up)) Used for setting various direction properties.  Is
equal to 1. 
dit(code(\voiceone)) Enter Voice context called code(one) and force stems down.
(See code(\stemdown).)
dit(code(\voicetwo)) Enter Voice context called code(two) and force stems
up. (See code(\stemup).)
dit(code(\voicethree)) Enter Voice context called code(three) and force stems
up.  
dit(code(\voicefour)) Enter Voice context called code(four), force stems down
and turn on horizontal shifting.  (See code(\stemdown) and code(\shifton).)
dit(code(\Wordwrap)) Used for setting the paper variable
code(castingalgorithm).  Equal to 0.0.  
)


sect(The code(\paper) Block)
label(paper)

The code(\paper) block may begin with an optional identifier reference.  No
identifier references are allowed anywhere else in the block.  
The keywords code(\shape), code(\)code(output) and code(\translator) may
appear in this block.  In addition, variable assignments may appear.  
The variables control layout details and are set to reasonable
defaults that depend on the font size in use.  The only way to find out what
variables are supported is to search the source code for code(get_var). 

subsect(Paper variables)

There are a large number of paper variables that are used to set internal
details of the layout.  Usually you will not want to change these variables.
Two variables that you may want to change are code(linewidth) and code(indent).

description(
  dit(var(integer)) If an integer appears on the left side of an
assignment then a code(\symboltables) keyword must appear on the right
side.  This defines a music font at a particular size.  See Voice
property code(\fontsize).

dit(code(arithmetic_basicspace) and code(arithmetic_multiplier))
The space taken by a note is determined by the formula 
verb(arithmetic_multiplier * ( c + time ))
where code(time) is the amount of time a note occupies.  The value of
code(c) is affected by code(arithmetic_basicspace).  Increasing
code(arithmetic_basicspace) will increase code(c).
dit(code(barsize)) Specify height of bars.  This value may need to be
adjusted if you change the number of lines in the staff.
dit(code(beam_dir_algorithm)) Specify algorithm for determining
whether beams go up or down.  It is real valued.  If set to 2.0 then
majority selection is used.  If set to 3.0, then mean selection is
used based on the mean center distance.  If set to 4.0 then median
selection is used, based on the median center distance.  
dit(code(beam_ideal_stem1))
dit(code(beam_ideal_stem2))
dit(code(beam_minimum_stem1))
dit(code(beam_minimum_stem2))
dit(code(beam_multiple_break))
dit(code(beam_slope_damp_correct_factor))
dit(code(beam_thickness)) Specify the thickness of beams.
dit(code(castingalgorithm)) 
dit(code(forced_stem_shorten)) Stems that have been forced to go the
unnatural direction are shortened by this amount.  Equal to
code(\interline) by default.  
dit(code(gourlay_energybound))
dit(code(gourlay_maxmeasures)) Maximum number of measures per line
when using Gourlay method.
Decreasing this greatly reduces computation time.  Default value: 10.  
dit(code(indent)) Sets the indentation of the first line of music.  
dit(code(interbeam))
dit(code(interbeam4))
dit(code(interline))  The distance between two staff
lines, calculated from the center of the lines.  
dit(code(linewidth))  Sets the width of the lines.  If it is set to
-1.0, then a single unjustified line is produced.  
dit(code(notewidth)) Width of an average note head.  
dit(code(rulethickness)) Determines thickness of staff lines and bars. 
dit(code(slur_clip_angle))
dit(code(slur_clip_height))
dit(code(slur_clip_ratio))
dit(code(slur_height_limit))
dit(code(slur_ratio))
dit(code(slur_rc_factor))
dit(code(slur_slope_damping))
dit(code(slur_thickness))
dit(code(slur_x_gap))
dit(code(slur_x_minimum))
dit(code(staffheight)) The height of the staff from the center of the
bottom line to the center of the top line.  Equal to to code(4 * \interline).
dit(code(stem_length)) Specify length of stems for notes in the staff
that don't have beams.  
dit(code(stemthickness)) Specifies the thickness of the stem lines.  
dit(code(tie_slope_damping))
dit(code(tie_x_minimum))
)

subsect(Translators)
label(translators)

The behavior of notation contexts is defined by the translators for
those contexts.  The translator for a context specifies what notations
are handled by the context, it specifies what other contexts the
context can contain, and it sets property values for the context.  The
default contexts are all defined in file(engraver.ly).  An easy way to
change the behavior of a context is to copy the definition from that
file and modify it.  

The first thing that appears inside a code(\translator)
definition is the type of the context being created.  There are 
four types:
description(
  dit(code(Engraver_group_engraver))
  dit(code(Hara_kiri_line_group_engraver))
  dit(code(Line_group_engraver_group))
  dit(code(Score_engraver))  
)
COMMENT( The names of these types seem somewhat confusing. )

After the type of the context is specified, property assignments and
code(\consists) and code(\accepts) keywords can appear in any order.  
Each code(\accepts) keyword specifies what contexts can be contained
inside this one.  

The code(\consists) keywords specify which notations are
handled by the context.  Each code(\consists) keyword specifies the
name of an engraver which handles a certain notation.  
Here is a list
of the engravers. 

description(
dit(code(Abbreviation_beam_engraver))
dit(code(Bar_column_engraver)) 
dit(code(Bar_engraver)) Engraves bar lines.  Normally in code(Staff) and
code(RhythmicStaff).  
dit(code(Bar_number_engraver)) Engrave bar numbers.  These numbers
appear at the start of each line.  Not normally in any translator.  Can
be added to code(Score) for Score-wide numbering or to code(Staff) for
numbering on each staff.  

dit(code(Beam_engraver)) Handles beam requests by engraving beams.  Normally
appears in the code(Voice) translator.  If omitted, then notes will be printed
with flags instead of beams.

dit(code(Beam_req_swallow_translator)) Swallows beam requests.  In
code(LyricVoice).  
dit(code(Clef_engraver)) Engraves the clef symbol.  Normally in code(Staff).
dit(code(Collision_engraver))
dit(code(Dot_column_engraver)) Engraves dots on dotted notes shifted to the
right of the note.  Normally in code(Voice).  If omitted, then dots appear on
top of the notes.  
dit(code(Dynamic_engraver)) Engraves dynamics symbols.  Normally in code(Voice).
dit(code(Font_size_engraver))
dit(code(Key_engraver)) Engraves the key signature.  Normally in code(Staff).
dit(code(Local_key_engraver))
dit(code(Lyric_engraver)) Engraves lyrics.  Normally in code(LyricVoice).
dit(code(Multi_measure_rest_engraver)) Engraves multi-measure rests that are
produced with code(R).  Normally in code(Voice).
dit(code(Note_heads_engraver)) Engraves note heads.  Normally in code(Voice).
Removing this gives a fatal error.  
COMMENT(Perhaps should be Note_head_engraver)
dit(code(Piano_bar_engraver))
dit(code(Pitch_squash_engraver)) Treat all pitches as middle C.  Used in
code(RhythmicStaff).  Note that the notes move, but the locations of
accidentals stay the same. 
dit(code(Plet_engraver)) Engraves brackets and the number over tuplets.  In
code(Voice).  
dit(code(Plet_swallow_engraver)) Swallows tuplet requests without any output.
In code(LyricVoice).  
COMMENT( Should this be named Plet_req_swallow_translator? )
dit(code(Priority_horizontal_align_engraver))
dit(code(Rest_collision_engraver)) Handles collisions of rests. In code(Staff).
dit(code(Rest_engraver)) Engraves rests.  Normally in code(Voice).
dit(code(Rhythmic_column_engraver))
dit(code(Score_priority_engraver))
dit(code(Script_engraver)) Handles note ornaments generated by code(\script).
Normally in code(Voice).  
dit(code(Separating_line_group_engraver))
dit(code(Skip_req_swallow_translator))
dit(code(Slur_engraver)) Engraves slurs.  Normally in code(Voice).
dit(code(Span_bar_engraver)) Engraves lines across multiple staffs.  Normally
in code(Staffgroup) and code(GrandStaff).  Removing this from code(StaffGroup)
gives the definition of code(ChoirStaff).  
dit(code(Span_score_bar_engraver))
dit(code(Staff_group_bar_engraver))
dit(code(Staff_margin_engraver)) Prints the name of the instrument
(specified by code(Staff.instrument) and code(Staff.instr)) at the
left of the staff.  
dit(code(Staff_sym_engraver))
dit(code(Stem_engraver)) Engraves stems.  Normally in code(Voice).
dit(code(Ties_engraver)) Engraves ties.  Normally in code(Voice).
COMMENT(perhaps should be named Tie_engraver?)
dit(code(Time_signature_engraver)) Engraves the time signature.  Normally in
code(Staff) and code(RhythmicStaff).
dit(code(Timing_engraver)) Responsible for synchronizing timing information
from staffs.  Normally in code(Score).  In order to create polyrhythmic music,
this engraver should be removed from code(Score) and placed in code(Staff).
dit(code(Vertical_align_engraver)) 
)