LilyPond — Changes
******************

This document lists changes and new features in LilyPond version 2.24.1
since 2.22.

          Note: LilyPond releases can contain syntax changes, which may
          require modifications in your existing files written for older
          versions so that they work in the new version.  To upgrade
          files, it is *strongly recommended* to use the ‘convert-ly’
          tool distributed with LilyPond, which is described in *note
          (lilypond-usage)Updating files with convert-ly::.
          ‘convert-ly’ can perform almost all syntax updates
          automatically.  Frescobaldi users can run ‘convert-ly’
          directly from Frescobaldi using “Tools > Update with
          convert-ly...”.  Other editing environments with LilyPond
          support may provide a way to run ‘convert-ly’ graphically.

Major changes in LilyPond
*************************

   • LilyPond now requires Guile 2.2.  Even if you are not writing
     Scheme code yourself, you may be using libraries that contain a
     non-trivial amount of customizations.  If they do not work with
     LilyPond version 2.24.1, please report this to the library’s
     developers.  If you _are_ a library developer, *note Notes on Guile
     2.2:: below.

   • The infrastructure for creating the official binaries has been
     completely rewritten, incident with the switch to Guile 2.2.  As of
     this release, we provide 64-bit binaries for macOS and Windows.
     Also, all packages are made available as simple archives that can
     be extracted to any “installation” location.  To uninstall, simply
     delete that directory.  We also discontinued the limited editor
     that was installed on macOS and Windows, LilyPad, and recommend
     switching to an external solution instead, such as the popular
     editor Frescobaldi (https://frescobaldi.org), or one of the others
     listed in *note (lilypond-web)Easier editing::.  For more
     information, please refer to the detailed instructions in *note
     (lilypond-learning)Installing::.

     The version of Ghostscript that ships in the official binaries no
     longer includes its own fonts, to reduce download size.  LilyPond
     does not need them (it has its own set of default fonts).  This
     does mean, however, that code such as ‘/Arial findfont’ in ‘\markup
     \postscript’ no longer works.  We recommend using normal ‘\markup’
     syntax to print glyphs.

Known issues in LilyPond 2.24.1
===============================

On Windows, compiling very large scores (several hundreds of pages) can
result in crashes.(1)  We hope to address this in a future 2.24.X
release.

   ---------- Footnotes ----------

   (1) Note that very large scores could already crash in LilyPond 2.22
due to restrictions imposed by the 32-bit architecture.

Notes for source compilation and packagers
==========================================

This section is aimed at enthusiasts compiling LilyPond from source and
packagers preparing LilyPond for distribution.  If you are not part of
either group, you can skip over this section.

   • As mentioned above, LilyPond now requires Guile 2.2.  If needed for
     distribution reasons, it can also be compiled with Guile 3.0 by
     passing ‘GUILE_FLAVOR=guile-3.0’ to the ‘configure’ script.
     However, this is not yet recommended nor officially supported.

   • The Scheme code evaluator in Guile 2.2 is slower than in Guile 1.X.
     To offset most of the performance penalty, we recommend compiling
     the ‘.scm’ files into bytecode by first running ‘make bytecode’
     during compilation and then ‘make install-bytecode’ in addition to
     ‘make install’.

   • Starting with this stable release, LilyPond’s build system does not
     install text fonts anymore.  Please provide them as separate
     packages while paying attention to the fonts’ license and notice
     files.

New for musical notation
************************

Pitches improvements
====================

   • Support for alternate accidentals was improved.  Through the
     ‘alterationGlyphs’ property of staff-like contexts, accidental
     glyphs may be set for all grobs at once (refer to *note
     (lilypond-notation)Alternate accidental glyphs::).

[[image of music]]

   • Ottava brackets may apply to a single voice instead of the entire
     staff.  This used to require workarounds.

          \layout {
            \context {
              \Staff
              \remove Ottava_spanner_engraver
            }
            \context {
              \Voice
              \consists Ottava_spanner_engraver
            }
          }

[[image of music]]

Rhythm improvements
===================

   • The new ‘\section’ command inserts a double bar line that interacts
     gracefully with repeat bar lines.  A passage can be named with the
     new ‘\sectionLabel’ command.

          \fixed c' {
            f1
            \break
            \section
            \sectionLabel "Trio"
            \repeat volta 2 {
              b1
            }
          }
[[image of music]]

   • ‘\numericTimeSignature’ and ‘\defaultTimeSignature’ now act on all
     staves at once (more precisely, on all staves in the same ‘Timing’
     context), thus matching the behavior of ‘\time’.

   • The ‘\rhythm’ markup command has been added.  It is a simple way to
     enter rhythms mixed with text, such as in “swing” indications.

          \relative {
            \tempo \markup {
              Swing
              \hspace #0.4
              \rhythm { 8[ 8] } = \rhythm { \tuplet 3/2 { 4 8 } }
            }
            b8 g' c, d ees d16 ees d c r8
          }
[[image of music]]

   • The ‘\enablePolymeter’ command is now provided as an input
     shorthand for moving engravers as is necessary to allow different
     time signatures in parallel.  The code:

          \layout {
            \context {
              \Score
              \remove Timing_translator
              \remove Default_bar_line_engraver
            }
            \context {
              \Staff
              \consists Timing_translator
              \consists Default_bar_line_engraver
            }
          }

     can thus be shortened as:

          \layout {
            \enablePolymeter
          }

     Independent of this, ‘Default_bar_line_engraver’ has been removed.

   • The new option ‘visible-over-note-heads’ can be used to make tuplet
     brackets always appear when their direction is set to be over the
     note heads.  It can be used with the default tuplet bracket
     visibility style or with ‘#'if-no-beam’.

[[image of music]]

   • Measure counts now take compressed multi-measure rests and
     alternatives into account.

[[image of music]]

   • Bar numbers may be centered in their measure, as is common in film
     scores.

          \layout {
            \context {
              \Score
              centerBarNumbers = ##t
              barNumberVisibility = #all-bar-numbers-visible
            }
          }

          <<
            { \repeat unfold 3 { c'4 d' e' f' } }
            { \repeat unfold 3 { c'4 d' e' f' } }
          >>
[[image of music]]

   • The alignment of bar numbers appearing in the middle or end of a
     system has been changed to align them on their left edge.  This is
     in keeping with the advice of Elaine Gould (‘Behind Bars’, p. 237),
     and was mostly the consensus reached in a discussion of the issue
     by developers.  The alignment of bars at the beginning of a system
     remains unchanged.

   • ‘\bar ","’ creates a short bar line.

[[image of music]]

   • The following predefined bar types no longer appear as a single bar
     line at the end of a line.  Annotated bar types (e.g., ‘\bar
     "S-|"’) have been added for that purpose.

[[image of music]]

   • ‘\bar ""’ is no longer necessary to print the first bar number.  It
     now suffices to set ‘barNumberVisibility’ to
     ‘all-bar-numbers-visible’, or one of the other visibility settings
     where the first bar number is visible.

     Note that this is a change in behavior for scores that set
     ‘barNumberVisibility’ to ‘all-bar-numbers-visible’ or such and
     ‘BarNumber.break-visibility’ to ‘#t’ without having ‘\bar ""’.
     Now, a bar number is printed at the beginning.  This is just the
     expected behavior (_all_ bar numbers should be visible), but due to
     slightly unclear documentation, users may have used these settings
     to print bar numbers in the middle of systems except for the first
     bar number.  In such cases, simply remove ‘\set
     Score.barNumberVisibility = #all-bar-numbers-visible’ since
     ‘\override BarNumber.break-visibility = ##t’ does the relevant
     setting alone.

   • The ‘\break’ command now always inserts a break, bypassing all
     default decisions about break points.  For example, it is no longer
     necessary to insert ‘\bar ""’ to obtain a mid-measure break.

     The new ‘\allowBreak’ command inserts a possible break point,
     without forcing it, but bypassing default decisions like ‘\break’
     does.

   • The bar line type ‘"-"’ has been removed.  ‘convert-ly’ converts it
     to ‘""’.  There is a slight difference in horizontal spacing at
     line breaks.

   • ‘automaticBars’ has been removed.  ‘convert-ly’ converts
     ‘automaticBars = ##f’ to ‘measureBarType = #'()’.

   • ‘\defineBarLine’ now accepts ‘#t’ in lieu of repeating the mid-line
     glyph name.

   • ‘Bar_engraver’ used to forbid line breaks between bar lines in all
     cases, but now it only does so when the
     ‘forbidBreakBetweenBarLines’ context property is set to ‘#t’, which
     is the default.  The ‘barAlways’ context property, which previously
     worked around the lack of ‘forbidBreakBetweenBarLines’, has been
     removed.

   • Due to changes in the internals of ‘\bar’, it is no longer
     supported to use it before creating lower contexts with ‘\new’.
     Such uses will now create an extra staff.  This is similar to what
     happens with commands such as ‘\override Staff...’ (see *note
     (lilypond-usage)An extra staff appears::).

          {
            \bar ".|:"
            <<
              \new Staff { c' }
              \new Staff { c' }
            >>
          }
[[image of music]]

     The solution is to place ‘\bar’ inside the music for each staff, as
     is usual with most commands.

          <<
            \new Staff { \bar ".|:" c' }
            \new Staff { \bar ".|:" c' }
          >>
[[image of music]]

   • The bar type ‘"-span|"’ creates a mensurstrich.

[[image of music]]

   • ‘Staff’ contexts use the new ‘Caesura_engraver’ to notate the
     ‘\caesura’ command.

[[image of music]]

Expressive mark improvements
============================

   • Events attached to notes (e.g., dynamics or articulations) can be
     delayed by an arbitrary duration using ‘\after’.  This simplifies
     many situations that previously required the use of explicit
     polyphony and spacer rests.

          {
            \after 2 \turn g'2. a'4
            \after 2 \< b'1
            \after 2. \f c''
            <>\< \after 4 \> \after 2\! d''
          }
[[image of music]]

   • Broken hairpins now have some left padding by default.  This is in
     line with published scores and it fixes some cases where broken
     hairpins were vertically displaced by the key signature.

          \relative {
            \key a \major
            c''4^\< c c c \break c c c c\! |
          }
[[image of music]]

   • The ends of hairpins may now be aligned to the ‘LEFT’, ‘CENTER’ or
     ‘RIGHT’ of ‘NoteColumn’ grobs by overriding the property
     ‘endpoint-alignments’.

[[image of music]]

   • The direction of a trill spanner can now be set with direction
     indicators like other articulations, i.e.  with ‘_\startTrillSpan’
     or ‘^\startTrillSpan’.

   • The default appearance of trill spanners has changed to better
     match classical engraving conventions.  They now end before the
     next note, not over it.  If the next note has an accidental, they
     stop before it.  If the next note is the first note of a measure,
     they stop over the bar line instead.

[[image of music]]

   • The padding by default for fermatas is now larger.  This avoids
     some cases where the fermata was placed too close to dots and other
     objects.

[[image of music]]

   • The flageolet symbol is now smaller and slightly thicker.  This is
     in line with published scores and makes the recommended workaround
     to make it smaller (‘\tweak font-size -3 \flageolet’) unnecessary.

[[image of music]]

   • The accent glyph is now a bit smaller.  This fixes some cases where
     a natural sign would vertically displace accents.

[[image of music]]

   • The comma glyph shape, as used in the ‘\breathe’ command, has been
     changed to a more common form.

[[image of music]]

     The old glyph remains available under the name ‘raltcomma’:

          {
            \override BreathingSign.text =
              \markup { \musicglyph "scripts.raltcomma" }
            f'2 \breathe f' |
          }
[[image of music]]

   • The new context property ‘breathMarkType’ selects the mark that
     ‘\breathe’ produces from several predefined types.

          \fixed c' {
            \set breathMarkType = #'tickmark
            c2 \breathe d2
          }
[[image of music]]

Repeat improvements
===================

   • Repeat alternatives may appear within the repeated section.

          \repeat volta 3 { c'1 \alternative { d' e' } f' }
[[image of music]]

   • The volta numbers for repeat alternatives may be set with the
     ‘\volta’ command.

          \repeat volta 3 c'1 \alternative { \volta 1 d' \volta 2,3 e' }
[[image of music]]

   • The new ‘\repeat segno’ command automatically notates a variety of
     _da-capo_ and _dal-segno_ forms.

          music = \fixed c' {
            \repeat segno 2 {
              b1
            }
            \fine
          }

          \score { \music }
          \score { \unfoldRepeats \music }
[[image of music]]

   • The new ‘\fine’ command inserts a final bar line that interacts
     gracefully with repeat bar lines.  Used inside ‘\repeat’, it also
     prints _Fine_ and ends the music after unfolding.

          music = \fixed c' {
            \repeat volta 2 {
              f1
              \volta 2 \fine
              \volta 1 b1
            }
          }

          \score { \music }
          \score { \unfoldRepeats \music }
[[image of music]]

   • The ‘\volta’ command removes music when a repeat is unfolded.

   • The ‘\unfolded’ command adds music when a repeat is unfolded.

Editorial annotation improvements
=================================

   • The new ‘\staffHighlight’ and ‘\stopStaffHighlight’ commands can be
     used to color a musical passage.

[[image of music]]

   • A new grob ‘FingerGlideSpanner’ is now available, indicating a
     finger gliding on a string from one to another position.  Several
     appearances are possible, depending on the setting of ‘style’.
     Shown in the image are ‘line’, ‘stub-left’, ‘stub-right’ and
     ‘stub-both’.

[[image of music]]

     Also possible is ‘dashed-line’, ‘dotted-line’, ‘zigzag’, ‘trill’,
     ‘bow’ and ‘none’.

   • Balloons now have changeable formatting.

[[image of music]]

   • Parenthesizing chords is supported.  Currently, the font size of
     the parentheses has to be adjusted manually.

[[image of music]]

   • Parenthesizing spanners is supported.

[[image of music]]

   • A “time-based” version of the ‘\parenthesize’ command was added.
     It takes a grob path: ‘\parenthesize GROBNAME’ or ‘\parenthesize
     CONTEXTNAME.GROBNAME’.  It acts like a ‘\once \override’.  This
     interface complements the already existing form ‘\parenthesize
     EVENT’, in a fashion similar to ‘\footnote’.

          {
            \parenthesize NoteHead
            c'1
            \parenthesize Staff.KeySignature
            \key g \major
            c'1
          }
[[image of music]]

   • Adding the ‘Melody_engraver’ to the ‘Voice’ context now works out
     of the box to change the stem direction of the middle note
     according to the melody.  Previously, this required an additional
     override to ‘Stem.neutral-direction’.

          \new Voice \with {
            \consists Melody_engraver
          }
          \relative c'' {
            \autoBeamOff
            g8 b a e g b a g |
            c b d c b e d c |
          }
[[image of music]]

     The ‘suspendMelodyDecisions’ context property may be used to turn
     off this behavior temporarily, as ‘\override Stem.neutral-direction
     = #DOWN’ used to do.

   • The new ‘Mark_tracking_translator’ takes over from ‘Mark_engraver’
     the decision of when to create a mark.  ‘Mark_engraver’ continues
     to control formatting and vertical placement.

     By default, ‘Mark_engravers’ in multiple contexts create a common
     sequence of marks.  If independent sequences are desired, multiple
     ‘Mark_tracking_translators’ must be used.

Text improvements
=================

   • New commands ‘\textMark’ and ‘\textEndMark’ are available to add an
     arbitrary piece of text between notes, called a text mark.  These
     commands improve over the previously existing syntax with the
     ‘\mark’ command called as ‘\mark MARKUP’ (i.e., ‘\mark "..."’ or
     ‘\mark \markup ...’).

          \fixed c' {
            \textMark "Text mark"
            c16 d e f e f e d c e d c e d c8
            \textEndMark "Text end mark"
          }
[[image of music]]

     ‘\textMark’ and ‘\textEndMark’ are now the recommended way to
     create textual marks.  The use of ‘\mark’ for this purpose is still
     supported, but discouraged (note that the ‘\mark’ command itself is
     not discouraged, only calling it on a markup argument; ‘\mark
     \default’ or ‘\mark NUMBER’ is still the recommended and only way
     to create a rehearsal mark).

     The new commands have several differences to ‘\mark MARKUP’.  There
     can be an arbitrary number of them at a given moment, while there
     can only be one use of ‘\mark’.  They output grobs of the dedicated
     ‘TextMark’ type, whereas ‘\mark’ creates a ‘RehearsalMark’ grob
     regardless of whether it is called for a rehearsal mark or a
     textual mark; introducing this distinction allows stylesheets to
     set different layout settings for rehearsal marks and text marks.
     The alignment set by the new commands is different: ‘\textMark’
     always creates a left-aligned mark, and ‘\textEndMark’ creates a
     right-aligned mark; in contrast, the alignment of a ‘RehearsalMark’
     depends on the anchor point of the object it aligns to.

     See *note (lilypond-notation)Text marks:: for full details.

   • Text variant glyphs for sharp, flat, natural, double sharp, and
     double flat are now available in the Emmentaler fonts.  In markup,
     they can be easily accessed with standard Unicode values.

[[image of music]]

   • It is now possible to control the width and the shape of (some)
     Emmentaler digits using OpenType features.

[[image of music]]

   • ‘\smallCaps’ now works on any markup, not just on a bare string.

   • The syntax for conditions in markups was made more flexible and
     user-friendly.  It uses the new markup commands ‘\if’ and
     ‘\unless’.  Here are example replacements:

     2.22 syntax                              2.24 syntax
     --------------------------------------------------------------------------------
     ‘\on-the-fly #first-page ...’            ‘\if \on-first-page ...’
     ‘\on-the-fly #not-part-first-page ...’   ‘\unless \on-first-page-of-part ...’
     ‘\on-the-fly #(on-page N) ...’           ‘\if \on-page #N ...’

   • With the new markup list command ‘string-lines’ it is now possible
     to split a string at a given character.  The default is to split at
     line break.  Surrounding white space gets dropped.  The resulting
     list of markups may be further formatted.  This is a very
     convenient way of entering additional stanzas for songs.

[[image of music]]

   • The new markup command ‘\align-on-other’ translates a markup as if
     it was aligned to another markup.

[[image of music]]

   • Two new markup functions ‘\with-dimension’ and
     ‘\with-dimension-from’ are available.  They are similar to
     ‘\with-dimensions’ and ‘\with-dimensions-from’, respectively,
     modifying only a single dimension (instead of both).

   • New markup commands ‘\with-true-dimension’ and
     ‘\with-true-dimensions’ are available.  They give the markup the
     actual extent(s) of its printed ink, which may differ from the
     default extents for some font glyphs due to text regularity
     constraints.

[[image of music]]

   • Text replacements can now replace strings with any markup, not just
     with a string.

          \markup
            \replace #`(("2nd" . ,#{ \markup \concat { 2 \super nd } #}))
            "2nd time"
[[image of music]]

   • A new markup command ‘\with-string-transformer’ is available.  It
     interprets a markup with a “string transformer” installed; the
     transformer is called when the interpretation of the markup
     requires interpreting a string, and allows to perform modifications
     on this string, such as changing case.

   • The ‘markup->string’ function converts a markup into an approximate
     string representation; it is used for outputting PDF metadata as
     well as MIDI lyrics and markers.  Markup commands can now define a
     custom method to convert markups created using them into strings,
     for use by ‘markup->string’.  For example:

          #(define-markup-command (upcase layout props arg) (string?)
             #:as-string (string-upcase arg)
             (interpret-markup layout props (string-upcase arg)))

New for specialist notation
***************************

Fretted string instrument improvements
======================================

   • The string tunings ‘banjo-double-c’ and ‘banjo-double-d’ were
     added.

   • A new grob ‘BendSpanner’ is now available for ‘TabStaff’,
     indicating a bent string.  Apart from the default three styles are
     possible: ‘'hold’, ‘'pre-bend’ and ‘'pre-bend-hold’.

[[image of music]]

Percussion improvements
=======================

   • The drum notation style ‘weinberg-drums-style’ was added.  It is
     based on Norman Weinberg’s standardization work.

Wind instrument improvements
============================

   • Additional display details of a ‘\woodwind-diagram’ can now be
     specified including the angle of partially-covered-keys and the
     display of non-graphical trill keys.

          \markup {
            \override #'(graphical . #f)
            \override #'(woodwind-diagram-details . ((fill-angle . 90)
                                                     (text-trill-circled . #f)))
            \woodwind-diagram #'flute #'((cc . (one1h))
                                         (lh . ())
                                         (rh . (besT)))
          }
[[image of music]]

Chord notation improvements
===========================

   • Support for chord grids has been added.

[[image of music]]

   • In ‘ChordNames’, multi-measure rests now also cause the “N.C.”
     symbol to be printed, just like normal rests.

   • In figured bass, ‘_’ now creates an empty figure that still takes
     up space.

          \figures {
            <8 _ 4]> <_ 5+ 3>
          }
[[image of music]]

   • Formatting of figured bass has been improved.  In particular, the
     default size is reduced to a value used by many Urtext editions of
     Baroque music.

   • In figured bass, specially designed glyphs for ‘6\\’, ‘7\\’, and
     ‘9\\’ are now used by default.  Similarly, specially designed
     glyphs for symbols ‘2\+’, ‘4\+’, and ‘5\+’ are used by default if
     plus signs appear after the number.

[[image of music]]

     Use the new command ‘\figured-bass’ to access these glyphs in
     markup.

   • In figured bass, brackets can now also be added around accidentals.

[[image of music]]

Ancient notation improvements
=============================

   • A new context ‘VaticanaLyrics’ is available.  It is similar to
     ‘Lyrics’, providing a hyphenation style (a single, flush-left
     hyphen between two syllables) as used in the notational style of
     Editio Vaticana.

   • The predefined commands for Gregorian divisiones are no longer
     variations on ‘\breathe’.  ‘\divisioMinima’, ‘\divisioMaior’,
     ‘\divisioMaxima’, and ‘\virgula’ are variations on the basic
     ‘\caesura’.  ‘\finalis’ is equivalent to ‘\section’.

     ‘MensuralStaff’ and ‘VaticanaStaff’ use ‘Divisio_engraver’ to
     interpret the above commands as well as ‘\repeat volta’ and
     ‘\fine’.

          \new MensuralStaff \fixed c' {
            \repeat volta 2 { f2 f }
            g1
            a1 \section
            b1 \fine
          }
[[image of music]]

   • ‘KievanStaff’, ‘MensuralStaff’, ‘PetrucciStaff’, and
     ‘VaticanaStaff’ now allow line breaks anywhere, and they no longer
     create ‘""’ measure bar lines.

   • In ‘GregorianTranscriptionStaff’, divisiones are now engraved as
     ‘BarLine’ grobs by default.  To change them to ‘Divisio’ grobs, use
     ‘\EnableGregorianDivisiones’.

   • ‘GregorianTranscriptionStaff’ allows a line break after any note
     and no longer uses ‘Time_signature_engraver’.

   • ‘GregorianTranscriptionVoice’ no longer uses ‘Stem_engraver’.

World music improvements
========================

   • Support for Persian classical music is now available.  For this,
     two accidental glyphs, _sori_ and _koron_, have been added to
     LilyPond.

          \include "persian.ly"

          \relative c' {
            \key d \chahargah
            bk'8 a gs fo r g ak g |
            fs ek d c d ef16 d c4 |
          }
[[image of music]]

Miscellaneous improvements
**************************

   • In the Emmentaler font, identical-looking noteheads whose only
     difference was stem direction have been consolidated into a single
     glyph.  For instance, the glyphs ‘noteheads.u2triangle’ and
     ‘noteheads.d2triangle’ have been replaced by a single glyph,
     ‘noteheads.s2triangle’.  Notehead pairs that look visually
     different depending on the direction remain distinct.

     In addition, the ‘stem-attachment’ property of ‘NoteHead’ grobs now
     returns its actual, direction-dependent stem attachment point
     instead of a hypothetical upwards-stem attachment point.

   • Two redundant glyphs in the Emmentaler font have been removed:
     ‘scripts.trillelement’ (use ‘scripts.trill_element’ instead) and
     ‘scripts.augmentum’ (use ‘dots.dotvaticana’ instead).

   • Using ‘\paper { bookpart-level-page-numbering = ##t}’, it is now
     possible to make bookparts independent with respect to page
     numbering.  If this is used for all bookparts, each bookpart has
     its own numbering sequence, starting at 1 by default.  It can also
     be used in an individual bookpart, which is useful to achieve the
     standard practice of numbers pages in an analytical introduction
     independently and in roman numerals (the latter is achieved using
     ‘page-number-type = #'roman-lower’).

   • A new grob callback function ‘break-alignment-list’ is now
     available for returning different values depending on a grob’s
     break direction.  As an example, use it to provide different
     alignments of a grob depending on whether it is positioned at the
     beginning, the middle, or the end of a line.

[[image of music]]

   • The new ‘Mark_performer’ creates MIDI Marker events like
     ‘Mark_engraver’ creates printed marks.

   • Properties of ‘PaperColumn’ and ‘NonMusicalPaperColumn’ (such as
     ‘NonMusicalPaperColumn.line-break-system-details’) can now be
     overridden mid-music with the usual command ‘\once \override’.
     They used to be a special case requiring the ‘\overrideProperty’
     command.

   • The new ‘show-horizontal-skylines’ and ‘show-vertical-skylines’
     properties allow to display an object’s skylines.  This is more
     flexible than the already existing ‘debug-skylines’ option because
     it works for all grobs.  While primarily meant for debugging
     LilyPond, this can be useful when trying to understand spacing
     decisions or overriding stencils in Scheme.

[[image of music]]

   • The new command ‘\vshape’ is like ‘\shape’, but also shows the
     control points and polygon for easier tweaking.

          { a1\vshape #'((0 . 0) (0 . 0.5) (0 . 0.9) (0 . 0.4))^( c'1) }
[[image of music]]

   • ‘\markup \path’ now also works in SVG output even if the path does
     not begin with a ‘moveto’ or ‘rmoveto’ command.  Also, it now
     accepts single-letter SVG equivalents (‘moveto’ = ‘M’, etc.).

   • ‘set-default-paper-size’ and ‘set-paper-size’ now accept a custom
     paper size.

          #(set-default-paper-size '(cons (* 100 mm) (* 50 mm)))

   • ‘lilypond-book’ supports two new music fragment options
     ‘paper-width’ and ‘paper-height’ to set a custom paper size.

   • ‘lilypond-book’ supports a new snippet option ‘inline’ for inline
     music, that is, music snippets like [[image of music]] that appear within a paragraph
     of text.

   • The ‘lilypond-book’ script now allows braces in the argument of the
     commands ‘\lilypond’ (for LaTeX) and ‘@lilypond’ (for Texinfo).

   • ‘lilypond-book’ now appends the current directory as the last entry
     to search for included files, instead of prepending it to the list
     of specified include paths.  This allows include directories to
     shadow files from the current directory, and will only be noticed
     if there are files with the same name in both.

   • The new Scheme function ‘universal-color’ provides an eight-element
     color palette designed to be unambiguous to people with
     dichromatism.

[[image of music]]

   • The ‘-dembed-source-code’ option now also embeds images added with
     ‘\epsfile’ and files included with ‘\verbatim-file’.

   • The default of the ‘aux-files’ program option changed to ‘#f’.  If
     you are calling LilyPond with the ‘-dbackend=eps’ argument and need
     the auxiliary ‘.tex’ and ‘.texi’ files, you now have to specify
     ‘-daux-files’ explicitly.  The formats for ‘lilypond-book’ images
     can be set separately for the tall page image (typically PNG for
     HTML output) and per-system images (typically, EPS or PDF for
     printed output) with the ‘-d’ sub-options ‘-dtall-page-formats’ and
     ‘-dseparate-page-formats’ respectively.

   • The ‘big point’ unit (1bp = 1/72in) is now available by appending
     ‘\bp’ to length values.

   • Scheme-defined translators usable in both ‘\layout’ and ‘\midi’ can
     now be created with ‘make-translator’.  Scheme-defined performers
     usable only in ‘\midi’ can now be created with ‘make-performer’.
     Those macros work strictly like the previously existing macro
     ‘make-engraver’ for creating engravers only usable in ‘\layout’.

   • Scheme translators can now define a new slot called
     ‘pre-process-music’.  It is called on all translators, after all
     listeners but before all ‘process-music’ slots.  This can be used
     for processing that depends on all events heard but needs to set
     context properties before other translators read them.

   • Scheme translators can now contain listeners written as

          (listeners
           ((event-class engraver event #:once)
            ...))

     These are never triggered more than once per time step.  They emit
     a warning if they receive two events in the same time step, except
     if the events are equal.

   • The same grob definition can now be used to create grobs of
     different classes (‘Item’, ‘Spanner’, ‘Paper_column’, ‘System’).
     As part of this change, the grob types ‘FootnoteItem’ and
     ‘FootnoteSpanner’ were consolidated into a single type ‘Footnote’.
     Similarly, ‘BalloonTextSpanner’ and ‘BalloonTextItem’ are unified
     into ‘BalloonText’.

     When the grob definition does not mandate a class, engravers should
     choose what class to create a grob with.  For authors of Scheme
     engravers, this means using either ‘ly:engraver-make-item’ or
     ‘ly:engraver-make-spanner’.  The utility function
     ‘ly:engraver-make-sticky’ is provided to support the frequent case
     of _sticky_ grobs, such as footnotes and balloons.  It creates a
     grob with the same class as another grob and administrates parents
     and bounds.

   • The new command-line option ‘-dcompile-scheme-code’, also settable
     in the LilyPond input with ‘#(ly:set-option 'compile-scheme-code)’,
     provides with better diagnostics when running Scheme code leads to
     an error.  Internally, this uses the byte-compiler provided by
     Guile, instead of the interpreter.

     However, due to a limitation in Guile, this currently has the
     disadvantage of making it impossible to run more than a few
     thousand Scheme expressions.  Also, be aware that the Guile
     compiler has a few differences to the interpreter.  For example,
     constant parts of quasiquotes are made actual constants more
     aggressively, making code such as ‘(let ((x 4)) (sort! `(,x 3 2
     1)))’ produce an error because the “cdr” of the quasiquoted list is
     constant, and it is an error in Scheme to mutate literal data.  (In
     this specific case, the code could avoid the issue by using the
     non-destructive ‘sort’, or by creating a fresh list each time with
     ‘(list x 3 2 1)’.)

     Furthermore, this option does not currently work on Windows.

Notes on Guile 2.2
******************

This version of LilyPond switches from Guile 1.8 to Guile 2.2.  This
section lists some of the most common incompatibilities that you could
have to deal with in order to upgrade your Scheme code.

   A full, detailed log of changes in Guile can be found in the ‘NEWS’
file (https://git.savannah.gnu.org/cgit/guile.git/tree/NEWS) of the
Guile source.

   • The ‘format’ function now requires a boolean or port as the first
     argument.  This argument was optional in Guile 1.8.  In order to
     make the function return the formatted output as a string, like
     ‘format’ does without this argument in Guile 1.8, pass ‘#f’ for
     this argument, i.e., ‘(format #f "STRING" ARGUMENTS ...)’ instead
     of ‘(format "STRING" ARGUMENTS ...)’.

   • The rules for internal (i.e., non-toplevel) definitions have become
     stricter.  Definitions are no longer allowed in various expression
     contexts.  This is no longer valid, for example:

          (if (not (defined? 'variable))
              (define variable 'value))

     The solution in this particular example is:

          (define variable
            (if (not (defined? 'variable))
                'value
                variable))

   • Strings now support Unicode characters.  Previously, a Unicode
     character was represented by several characters, and various
     functions were not tailored for Unicode support.

   • Some numeric functions now return exact results in more cases.  For
     instance, ‘(sqrt 4)’ returns ‘2.0’ in Guile 1.8, but ‘2’ (an
     integer) in Guile 2.2.

