* Documentation/user/preface.itely: small bits

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

@c -*-texinfo-*-

@node Introduction
@chapter Introduction


LilyPond is a program to print sheet music. If you have used notation
programs before, then the way to use this program might be surprising
at first sight. To print music with lilypond, you have to enter
musical codes in a file. Then you run LilyPond on the file, and the
music is produced without any intervention. For example, something
like this:

@lilypond[fragment,verbatim, relative 1, intertext="produces this"]
\key c \minor r8 c16 b c8 g as c16 b c8 d | g,4 
@end lilypond

@cindex encoding music

Encoding music using letters and digits may appear strange,
intimidating or even clumsy at first. Nevertheless, when you take the
effort to learn the codes and the program you will find that it is
easier than it seems.  Entering music can be done quickly, and you
never have to remember how you made the program do something
complicated: it's all in the input code, and you only have to read the
file to see how it works. Moreover, when you use LilyPond, you are
rewarded with very nicely looking output.

In this Chapter, we will try to explain what we are trying to do with
LilyPond, how this lead to its current form, and how this approach
affects you as a user.


@menu
* Batch processing::            
* Music engraving::             
* Music representation::        
* About this manual::           
@end menu

@node Batch processing
@section Batch processing

@cindex GUI
@cindex Batch
@cindex UNIX 

When we started with developing LilyPond, we were interested in music
notation, not as publishers or musicians, but as students and
scientists. We wanted tried to figure to what extent formatting sheet
music could be automated.  This was when we were still studying at the
university. Back then GUIs were not as ubiquitous as they are today,
and we were immersed in the UNIX operating system, where it is very
common to use compilers to achieve computing tasks, so our
computerized music engraving experiment took on the form of a
compiler.

@cindex free software
@cindex sharing software

One other decision was also motivated by our academic background. In
the scientific community it has always been a tradition to share
knowledge, and, to a lesser extent, the software you wrote. One of the
most visible groups that stimulated this philosopy, was the Free
Software Foundation, whose GNU project aimed to replace closed and
proprietary computing solutions with free (as in ``Libre'')
variants. We jumped on that bandwagon, and that is the reason that you
can still get LilyPond at no cost without any strings attached.


@node Music engraving
@section Music engraving



@cindex engraving
@cindex typography

Making sheet music may seem trivial at first (``you print 5 lines, and
then put in the notes at different heights''), @emph{music engraving},
i.e. professional music typography, is in another ballpark.  The term
music engraving derives from the traditional process of music
printing.  Only a few decades ago, sheet music was made by cutting and
stamping the music mirrored into zinc or pewter plates. The plate
would be inked, and the depressions caused by the cutting and stamping
would hold ink.  A positive image was formed by pressing paper to the
plate. Stamping and cutting was completely done by hand, and making
corrections was cumbersome, so engraving had to be correct in one
go. As you can imagine this was a highly specialized skill, much more
so than the traditional process of printing books.

@cindex craftmanship
@cindex master

In fact, in the traditional German craftmanship six years of full-time
training were required, before a student could call himself a master
of the art. After that many more years of practical experience were
needed to become an established music engraver.  Even today, in the
era of high-speed computers, music requires lots of manual fine tuning
before it acceptable to be published.

When we wanted to write a computer program to do create music
typography, we encountered the first problem: there were no sets of
musical symbols available: either they were not available freely, or
they didn't look well to our taste. That was the reason for us to
create a font of musical symbols, relying mostly on nice printouts of
hand-engraved music.  It was a good decision to design our own
font. The experience helps develop a typographical taste, and it makes
one appreciate subtle design details. Without that experience, we
would not have realized how ugly the fonts were that we admired at
first.


@lilypond
#(define magfact 3.0)
\score {  \notes { as'2 r4 }
          \paper {
              linewidth = -1. 
              \translator {
                  \ScoreContext
                  AccidentalPlacement \override #'right-padding = #3.0
                  StaffSymbol \override #'transparent =   ##t
                  Clef \override #'transparent = ##t
                  TimeSignature \override #'transparent = ##t             
                  Accidental \override #'font-magnification = #magfact
                  Rest \override #'font-magnification = #magfact
                  NoteHead \override #'font-magnification = #magfact
                  Stem \override #'transparent = ##t
                  } } }
@end lilypond

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

The figure above shows a few notable glyphs. For example, the
half-notehead is not elliptic but slightly diamond shaped.  The stem
of a flat symbol should be slightly brushed, i.e. becoming wider at
the top. Fine endings, such as the one on the bottom of the quarter
rest, should not end in sharp points, but rather in rounded shapes.
Taken together, the blackness of the font must be carefully tuned
together with the thickness of lines, beams and slurs to give a strong
yet balanced overall impression.

Producing a strong and balanced look is the real challenge of music
engraving. It is a recurring theme with many variations. One of these
variations is choosing spacing. The distances between notes should
reflect the durations between notes, but adhering with mathematical
precision to the duration will lead to a poor result. Shown here is an
example of a motive, printed four times. It is printed using both
exact, mathematical spacing, and with some corrections. Can you spot
which is which?

@cindex optical spacing
@lilypond
    \score { \notes {
      \property Staff.NoteSpacing \set #'stem-spacing-correction
        = #0.6
      c'4 e''4 e'4 b'4 |
      b'4 e''4 b'4 e''4|
      \property Staff.NoteSpacing \override #'stem-spacing-correction
      = #0.0
      \property Staff.StaffSpacing \override #'stem-spacing-correction
      = #0.0
      c'4 e''4 e'4 b'4 |
      b'4 e''4 b'4 e''4|      
    }
    \paper { linewidth = -1. } }
@end lilypond

@cindex regular rhythms
@cindex regular spacing

The fragment that was printed uses only quarter notes: notes that are
played in a constant regular rhythm. The spacing should reflect
that. Unfortunately, the eye deceives us a little: the eye not only
notices the distance between note heads, but also between consecutive
stems. Depending on the different vertical positions, the notes of a
upstem-downstem combination should be put farther apart, and the notes
of a down-up combination should be put closer together. The first two
measures are printed with this correction, the last two measures
without. The notes in the last two measures form downstem/upstems
clumps of notes.

We hope that these examples serve to show that music typography is a
subtle business, and that it requires skill and knowledge to produce
good engraving.  It was our challenge to see if we could put such
knowledge into a computer program.


@node Music representation
@section Music representation


One of the first questions that pop up when you design such a program,
is what kind of input the program should expect. Many music notation
programs offer a graphical interface that shows notation, and allow
you to enter the music by placing notes on a staff. Although this is a
obvious way to design a program, from our point of view, this is
cheating. After all, the core message of a piece of music notation
simply is the music itself. If you start by offering notation to the
user, you have already skipped one conversion, even if it perhaps is
implicit. If we want to generate music notation from something else,
then the obvious candidate for the source should be the music itself.

Of course, on paper this theory sounds very good. In practice, it
opens a can of worms. What really @emph{is} music? Many philosophical
treatises must have been written on the subject. Even if you are more
practically inclined, you will notice that an enormous number of
different ways to represent music in a computer exist, and they are
much more incompatible than the formats for wordprocessors and
spreadsheets.  Anyone who has tried to exchange data files from
between different notation programs can attest to this.

@cindex music representation
@cindex music expressions
@cindex input format

The cause of this problem is that music is inherently two-dimensional:
in polyphonic music, notes have time and pitch as their two
coordinates, and they often are related in both directions. Computer
files on the other hand are essentially one-dimensional: they are a
long stream of characters. When you represent music in a file, then
you have to flatten this two-dimensional information breaking either
timing or pitch relations, and there is no universal agreement on how
to do this.

Luckily, our application has guided us a little with the design of the
format: we want to produce a printed score from a music
representation.  A music representation is about @emph{music}, so it
should be free from notation as much as possible: the format is about
pitches and durations, not about symbols and offsets.  Since LilyPond
is a compiler, the input format is its user interface, and users have
to key in the music into the file directly, requiring that the input
format has a friendly syntax. We, as programmers and scientists want a
clean formal definition. After all, producing music notation is a
difficult problem, and in the scientific world, difficult problems
always must be well-specified. Moreover, formally defined formats are
easier to write programs for. Finally, enough information should be
present to be able to produce a printed score.

These ideas shaped our music representation which elegantly builds
complex musical constructs from simple entities like notes and rests,
in much the same way that one builds complex formulae from simple
expressions such as numbers and mathematical operators.  The strict
separation between musical information and typesetting also gives a
blueprint of the program: first it reads the music representation,
then it interprets the music---reading it `left-to-right', and
translating the musical information to a layout specification. When
the layout is computed, the resulting symbols are written to an output
file.


@node About this manual
@section About this manual



As you will notice in the coming pages, and the examples, in a lot of
case, the program makes good decisions, and what comes out of lilypond
generally looks good. For some specific examples, the default layout
of lilypond even is suitable for publication. However, some aspects of
the formatting are not yet very good. This gives us programmers
inspiration for improving the program. However, most users are more
interested in making their printouts look good, and then they have to
make manual adjustments to the output.  Another aspect of our system
of encoding through ASCII then shows: it can be complicated to fine
tune the layout of a piece. There is no graphical user interface,
where you can simply click and drag a symbol. On the other hand, if
you have written the code for tuning one specific aspect of the
layout, then you can simply store the file on disk, retrieve it when
you need it: there is no need to remember how you did it.  It's all in
the input file. Lilypond also comes with a huge collection of snippets
that show all kinds of tricks.

@cindex snippets
@cindex adjusting output


This collection is much needed, because of the way LilyPond is
structured. It is a large program, but almost all of the internal
functionality is exported: that is, the variables that are internally
used to determine formatting of the sheet music are available directly
to the user. These are variables to control thicknesses, distances,
and other formatting options: there are a huge number of them, and it
would be impossible to describe them all in a hand-written
manual. There is no need to despair, there is `automatic' manual, that
lists all of the variables, symbol types, etc. that are available.  It
is directly generated from the definitions that LilyPond itself uses,
so it is always up to date. If you are reading this from a screen: it
is available from the web, and is included with most binary
distributions.  If you're reading this from paper, then we advise you
to use the digital version anyway: the hyperlinks make finding topics
in the lilypond-internals manual much easier.

@cindex variables
@cindex properties
@cindex lilypond-internals
@cindex internal documentation 

For those who really want to get their hands dirty: it is even
possible to add your own functionality, by extending LilyPond in the
built-in scripting language, a dialect of the powerful programming
language Scheme. There is no real distinction between what a user can
do and what a programmer is allowed to do.

@cindex Scheme
@cindex extending lilypond

In short, this manual does not pretend to be exhaustive, but it is
merely a guide that tries to explain the most important principles,
and shows popular input idioms.  The rest of the manual is structured
as follows: it starts with a tutorial that explains how to use
lilypond. In the tutorial, a number of fragments of increasing
complexity are shown and explained.  Then comes the reference manual,
which gives more detailed information on all features of If you're new
to lilypond, then you should start reading the tutorial, and
experiment for yourself.  If you already have some experience, then
you can simply use the manual as reference: there is an extensive
index@footnote{If you are looking something, and you can't find it by
using the index, that is considered a bug.  In that case, please file
a bugreport}

@cindex bugreport
@cindex index
@cindex tutorial
@cindex overview of manual
@cindex idiom