% -*-Scheme-*-

\version "2.12.0"


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% this file is alphabetically sorted.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% need SRFI-1 for filter; optargs for lambda*
#(use-modules (srfi srfi-1)
	      (ice-9 optargs))

%% TODO: using define-music-function in a .scm causes crash.

acciaccatura =
#(def-grace-function startAcciaccaturaMusic stopAcciaccaturaMusic
   (_i "Create an acciaccatura from the following music expression"))

%% keep these two together
"instrument-definitions" = #'()
addInstrumentDefinition =
#(define-music-function
   (parser location name lst) (string? list?)
   (_i "Create instrument @var{name} with properties @var{list}.")
   (set! instrument-definitions (acons name lst instrument-definitions))
   (make-music 'SequentialMusic 'void #t))

addQuote =
#(define-music-function (parser location name music) (string? ly:music?)
   (_i "Define @var{music} as a quotable music expression named
@var{name}")
   (add-quotable parser name music)
   (make-music 'SequentialMusic 'void #t))

%% keep these two together
afterGraceFraction = #(cons 6 8)
afterGrace =
#(define-music-function
  (parser location main grace)
  (ly:music? ly:music?)
  (_i "Create @var{grace} note(s) after a @var{main} music expression.")
  (let*
      ((main-length (ly:music-length main))
       (fraction  (ly:parser-lookup parser 'afterGraceFraction)))

    (make-simultaneous-music
     (list
      main
      (make-sequential-music
       (list

	(make-music 'SkipMusic
		    'duration (ly:make-duration
			       0 0
			       (* (ly:moment-main-numerator main-length)
				  (car fraction))
			       (* (ly:moment-main-denominator main-length)
				  (cdr fraction)) ))
	(make-music 'GraceMusic
		    'element grace)))))))


%% music identifiers not allowed at top-level,
%% so this is a music-function instead.
allowPageTurn =
#(define-music-function (location parser) ()
   (_i "Allow a page turn. May be used at toplevel (ie between scores or
markups), or inside a score.")
   (make-music 'EventChord
	       'page-marker #t
	       'page-turn-permission 'allow
	       'elements (list (make-music 'PageTurnEvent
					   'break-permission 'allow))))

applyContext =
#(define-music-function (parser location proc) (procedure?)
  (_i "Modify context properties with Scheme procedure @var{proc}.")
  (make-music 'ApplyContext
	      'origin location
	      'procedure proc))

applyMusic =
#(define-music-function (parser location func music) (procedure? ly:music?)
   (_i"Apply procedure @var{func} to @var{music}.")
  (func music))

applyOutput =
#(define-music-function (parser location ctx proc) (symbol? procedure?)
  (_i "Apply function @code{proc} to every layout object in context @code{ctx}")
  (make-music 'ApplyOutputEvent
	      'origin location
	      'procedure proc
	      'context-type ctx))

appoggiatura =
#(def-grace-function startAppoggiaturaMusic stopAppoggiaturaMusic
  (_i "Create an appoggiatura from @var{music}"))

% for regression testing purposes.
assertBeamQuant =
#(define-music-function (parser location l r) (pair? pair?)
  (_i "Testing function: check whether the beam quants @var{l} and @var{r} are correct")
  (make-grob-property-override 'Beam 'positions
   (ly:make-simple-closure
    (ly:make-simple-closure
     (append
      (list chain-grob-member-functions `(,cons 0 0))
      (check-quant-callbacks l r))))))

% for regression testing purposes.
assertBeamSlope =
#(define-music-function (parser location comp) (procedure?)
  (_i "Testing function: check whether the slope of the beam is the same as @code{comp}")
  (make-grob-property-override 'Beam 'positions
   (ly:make-simple-closure
    (ly:make-simple-closure
     (append
      (list chain-grob-member-functions `(,cons 0 0))
      (check-slope-callbacks comp))))))

autochange =
#(define-music-function (parser location music) (ly:music?)
  (_i "Make voices that switch between staves automatically")
  (make-autochange-music parser music))



balloonGrobText =
#(define-music-function (parser location grob-name offset text)
			(symbol? number-pair? markup?)
  (_i "Attach @var{text} to @var{grob-name} at offset @var{offset}
(use like @code{\\once})")
    (make-music 'AnnotateOutputEvent
		'symbol grob-name
		'X-offset (car offset)
		'Y-offset (cdr offset)
		'text text))

balloonText =
#(define-music-function (parser location offset text) (number-pair? markup?)
  (_i "Attach @var{text} at @var{offset} (use like @code{\\tweak})")
    (make-music 'AnnotateOutputEvent
		'X-offset (car offset)
		'Y-offset (cdr offset)
		'text text))

bar =
#(define-music-function (parser location type) (string?)
  (_i "Insert a bar line of type @var{type}")
   (context-spec-music
    (make-property-set 'whichBar type)
    'Timing))

barNumberCheck =
#(define-music-function (parser location n) (integer?)
  (_i "Print a warning if the current bar number is not @var{n}.")
   (make-music 'ApplyContext
	       'origin location
	       'procedure
	       (lambda (c)
		 (let*
		     ((cbn (ly:context-property c 'currentBarNumber)))
		   (if (and  (number? cbn) (not (= cbn n)))
		       (ly:input-message location "Barcheck failed got ~a expect ~a"
					 cbn n))))))

bendAfter =
#(define-music-function (parser location delta) (real?)
  (_i "Create a fall or doit of pitch interval @var{delta}.")
  (make-music 'BendAfterEvent
   'delta-step delta))

%% why a function?
breathe =
#(define-music-function (parser location) ()
  (_i "Insert a breath mark.")
	    (make-music 'EventChord
	      'origin location
	      'elements (list (make-music 'BreathingEvent))))



clef =
#(define-music-function (parser location type) (string?)
  (_i "Set the current clef to @var{type}.")
   (make-clef-set type))

cueDuring =
#(define-music-function
  (parser location what dir main-music) (string? ly:dir? ly:music?)
  (_i "Insert contents of quote @var{what} corresponding to @var{main-music},
in a CueVoice oriented by @var{dir}.")
  (make-music 'QuoteMusic
	      'element main-music
	      'quoted-context-type 'Voice
	      'quoted-context-id "cue"
	      'quoted-music-name what
	      'quoted-voice-direction dir
	      'origin location))



displayLilyMusic =
#(define-music-function (parser location music) (ly:music?)
  (_i "Display	the LilyPond input representation of @var{music}
to the console.")
   (newline)
   (display-lily-music music parser)
   music)

displayMusic =
#(define-music-function (parser location music) (ly:music?)
  (_i "Display the internal representation of @var{music} to the console.")
   (newline)
   (display-scheme-music music)
   music)



endSpanners =
#(define-music-function (parser location music) (ly:music?)
  (_i "Terminate the next spanner prematurely after exactly one note without the need of a specific end spanner.")
   (if (eq? (ly:music-property music 'name) 'EventChord)
       (let*
	   ((elts (ly:music-property music 'elements))
	    (start-span-evs (filter (lambda (ev)
				(and (music-has-type ev 'span-event)
				     (equal? (ly:music-property ev 'span-direction)
					     START)))
			      elts))
	    (stop-span-evs
	     (map (lambda (m)
		    (let* ((c (music-clone m)))
		      (set! (ly:music-property c 'span-direction) STOP)
		      c))
		  start-span-evs))
	    (end-ev-chord (make-music 'EventChord
				      'elements stop-span-evs))
	    (total (make-music 'SequentialMusic
			       'elements (list music
					       end-ev-chord))))
	 total)

       (ly:input-message location (_ "argument endSpanners is not an EventChord: ~a" music))))



featherDurations=
#(define-music-function (parser location factor argument) (ly:moment? ly:music?)
 (_i "Adjust durations of music in @var{argument} by rational @var{factor}. ")
   (let*
       ((orig-duration (ly:music-length argument))
	(multiplier (ly:make-moment 1 1)))

     (music-map
      (lambda (mus)
	(if (and (eq? (ly:music-property mus 'name) 'EventChord)
		 (< 0 (ly:moment-main-denominator (ly:music-length mus))))
	    (begin
	      (ly:music-compress mus multiplier)
	      (set! multiplier (ly:moment-mul factor multiplier)))
	    )
	mus)
      argument)

     (ly:music-compress
      argument
      (ly:moment-div orig-duration (ly:music-length argument)))

     argument))



grace =
#(def-grace-function startGraceMusic stopGraceMusic
   (_i "Insert @var{music} as grace notes."))



instrumentSwitch =
#(define-music-function
   (parser location name) (string?)
   (_i "Switch instrument to @var{name}, which must be predefined with
@code{\\addInstrumentDefinition}.")
   (let*
       ((handle	 (assoc name instrument-definitions))
	(instrument-def (if handle (cdr handle) '()))
	)

     (if (not handle)
	 (ly:input-message location "No such instrument: ~a" name))
     (context-spec-music
      (make-music 'SimultaneousMusic
		  'elements
		  (map (lambda (kv)
			 (make-property-set
			  (car kv)
			  (cdr kv)))
		       instrument-def))
      'Staff)))



keepWithTag =
#(define-music-function
  (parser location tag music) (symbol? ly:music?)
  (_i "Include only elements of @var{music} that are tagged with @var{tag}.")
  (music-filter
   (lambda (m)
    (let* ((tags (ly:music-property m 'tags))
	   (res (memq tag tags)))
     (or
      (eq? tags '())
      res)))
   music))

killCues =
#(define-music-function
   (parser location music)
   (ly:music?)
   (_i "Remove cue notes from @var{music}.")
   (music-map
    (lambda (mus)
      (if (and (string? (ly:music-property mus 'quoted-music-name))
	       (string=? (ly:music-property mus 'quoted-context-id "") "cue"))
	  (ly:music-property mus 'element)
	  mus)) music))



label =
#(define-music-function (parser location label) (symbol?)
   (_i "Create @var{label} as a bookmarking label")
   (make-music 'EventChord
	       'page-marker #t
	       'page-label label
	       'elements (list (make-music 'LabelEvent
					   'page-label label))))



makeClusters =
#(define-music-function
		(parser location arg) (ly:music?)
   (_i "Display chords in @var{arg} as clusters")
		(music-map note-to-cluster arg))

musicMap =
#(define-music-function (parser location proc mus) (procedure? ly:music?)
	     (music-map proc mus))



%% noPageBreak and noPageTurn are music functions (not music indentifiers),
%% because music identifiers are not allowed at top-level.
noPageBreak =
#(define-music-function (location parser) ()
   (_i "Forbid a page break. May be used at toplevel (ie between scores or
markups), or inside a score.")
   (make-music 'EventChord
	       'page-marker #t
	       'page-break-permission 'forbid
	       'elements (list (make-music 'PageBreakEvent
					   'break-permission '()))))

noPageTurn =
#(define-music-function (location parser) ()
   (_i "Forbid a page turn. May be used at toplevel (ie between scores or
markups), or inside a score.")
   (make-music 'EventChord
	       'page-marker #t
	       'page-turn-permission 'forbid
	       'elements (list (make-music 'PageTurnEvent
					   'break-permission '()))))



octaveCheck =
#(define-music-function (parser location pitch-note) (ly:music?)
   (_i "octave check")

   (make-music 'RelativeOctaveCheck
	       'origin location
	       'pitch (pitch-of-note pitch-note)
	   ))

ottava = #(define-music-function (parser location octave) (number?)
  (_i "set the octavation ")
  (make-ottava-set octave))

overrideBeamSettings =
#(define-music-function
    (parser location
     context time-signature rule-type grouping-rule)
    (symbol? pair? symbol? pair?)

 (_i "Override beamSettings in @var{context}
for time signatures of @var{time-signature} and rules of type
@var{rule-type} to have a grouping rule alist
@var{grouping-rule}.
@var{rule-type} can be @code{end} or @code{subdivide},
with a potential future value of @code{begin}.
@var{grouping-rule} is an alist of @var{(beam-type . grouping)}
entries.  @var{grouping} is in units of @var{beam-type}.  If
@var{beam-type} is @code{*}, grouping is in units of the denominator
of @var{time-signature}.")

 ;; TODO -- add warning if largest value of grouping is
 ;;	    greater than time-signature.

#{
#(override-beam-setting
  $time-signature $rule-type $grouping-rule $context)
#})

overrideProperty =
#(define-music-function (parser location name property value)
   (string? symbol? scheme?)

   (_i "Set @var{property} to @var{value} in all grobs named @var{name}.
The @var{name} argument is a string of the form @code{\"Context.GrobName\"}
or @code{\"GrobName\"}")

   (let*
       ((name-components (string-split name #\.))
	(context-name 'Bottom)
	(grob-name #f))

     (if (> 2 (length name-components))
	 (set! grob-name (string->symbol (car name-components)))
	 (begin
	   (set! grob-name (string->symbol (list-ref name-components 1)))
	   (set! context-name (string->symbol (list-ref name-components 0)))))

     (make-music 'ApplyOutputEvent
		 'origin location
		 'context-type context-name
		 'procedure
		 (lambda (grob orig-context context)
		   (if (equal?
			(cdr (assoc 'name (ly:grob-property grob 'meta)))
			grob-name)
		       (set! (ly:grob-property grob property) value))))))



%% pageBreak and pageTurn are music functions (iso music indentifiers),
%% because music identifiers are not allowed at top-level.
pageBreak =
#(define-music-function (location parser) ()
   (_i "Force a page break. May be used at toplevel (i.e. between scores or
markups), or inside a score.")
   (make-music 'EventChord
	       'page-marker #t
	       'line-break-permission 'force
	       'page-break-permission 'force
	       'elements (list (make-music 'LineBreakEvent
					   'break-permission 'force)
			       (make-music 'PageBreakEvent
					   'break-permission 'force))))

pageTurn =
#(define-music-function (location parser) ()
   (_i "Force a page turn between two scores or top-level markups.")
   (make-music 'EventChord
	       'page-marker #t
	       'line-break-permission 'force
	       'page-break-permission 'force
	       'page-turn-permission 'force
	       'elements (list (make-music 'LineBreakEvent
					   'break-permission 'force)
			       (make-music 'PageBreakEvent
					   'break-permission 'force)
			       (make-music 'PageTurnEvent
					   'break-permission 'force))))

parallelMusic =
#(define-music-function (parser location voice-ids music) (list? ly:music?)
  (_i "Define parallel music sequences, separated by '|' (bar check signs),
and assign them to the identifiers provided in @var{voice-ids}.

@var{voice-ids}: a list of music identifiers (symbols containing only letters)

@var{music}: a music sequence, containing BarChecks as limiting expressions.

Example:

@verbatim
  \\parallelMusic #'(A B C) {
    c c | d d | e e |
    d d | e e | f f |
  }
<==>
  A = { c c | d d | }
  B = { d d | e e | }
  C = { e e | f f | }
@end verbatim
")
  (let* ((voices (apply circular-list (make-list (length voice-ids) (list))))
	 (current-voices voices)
	 (current-sequence (list)))
    ;;
    ;; utilities
    (define (push-music m)
      "Push the music expression into the current sequence"
      (set! current-sequence (cons m current-sequence)))
    (define (change-voice)
      "Stores the previously built sequence into the current voice and
       change to the following voice."
      (list-set! current-voices 0 (cons (make-music 'SequentialMusic
					 'elements (reverse! current-sequence))
					(car current-voices)))
      (set! current-sequence (list))
      (set! current-voices (cdr current-voices)))
    (define (bar-check? m)
      "Checks whether m is a bar check."
      (eq? (ly:music-property m 'name) 'BarCheck))
    (define (music-origin music)
      "Recursively search an origin location stored in music."
      (cond ((null? music) #f)
	    ((not (null? (ly:music-property music 'origin)))
	     (ly:music-property music 'origin))
	    (else (or (music-origin (ly:music-property music 'element))
		      (let ((origins (remove not (map music-origin
						      (ly:music-property music 'elements)))))
			(and (not (null? origins)) (car origins)))))))
    ;;
    ;; first, split the music and fill in voices
    (map-in-order (lambda (m)
		    (push-music m)
		    (if (bar-check? m) (change-voice)))
		  (ly:music-property music 'elements))
    (if (not (null? current-sequence)) (change-voice))
    ;; un-circularize `voices' and reorder the voices
    (set! voices (map-in-order (lambda (dummy seqs)
				 (reverse! seqs))
			       voice-ids voices))
    ;;
    ;; set origin location of each sequence in each voice
    ;; for better type error tracking
    (for-each (lambda (voice)
		(for-each (lambda (seq)
			    (set! (ly:music-property seq 'origin)
				  (or (music-origin seq) location)))
			  voice))
	      voices)
    ;;
    ;; check sequence length
    (apply for-each (lambda* (#:rest seqs)
		      (let ((moment-reference (ly:music-length (car seqs))))
			(for-each (lambda (seq moment)
				    (if (not (equal? moment moment-reference))
					(ly:music-message seq
					 "Bars in parallel music don't have the same length")))
			  seqs (map-in-order ly:music-length seqs))))
	   voices)
   ;;
   ;; bind voice identifiers to the voices
   (map (lambda (voice-id voice)
	  (ly:parser-define! parser voice-id
			     (make-music 'SequentialMusic
			       'origin location
			       'elements voice)))
	voice-ids voices))
 ;; Return an empty sequence. this function is actually a "void" function.
 (make-music 'SequentialMusic 'void #t))

parenthesize =
#(define-music-function (parser loc arg) (ly:music?)
   (_i "Tag @var{arg} to be parenthesized.")

   (if (memq 'event-chord (ly:music-property arg 'types))
     ; arg is an EventChord -> set the parenthesize property on all child notes and rests
     (map
       (lambda (ev)
	 (if (or (memq 'note-event (ly:music-property ev 'types))
		 (memq 'rest-event (ly:music-property ev 'types)))
	   (set! (ly:music-property ev 'parenthesize) #t)))
       (ly:music-property arg 'elements))
     ; No chord, simply set property for this expression:
     (set! (ly:music-property arg 'parenthesize) #t))
   arg)

partcombine =
#(define-music-function (parser location part1 part2) (ly:music? ly:music?)
   (_i "Take the music in @var{part1} and @var{part2} and typeset so that they share a staff.")
   (make-part-combine-music parser
			    (list part1 part2)))

pitchedTrill =
#(define-music-function
   (parser location main-note secondary-note)
   (ly:music? ly:music?)
   (_i "Print a trill with @var{main-note} as the main note of the trill and
print @var{secondary-note} as a stemless note head in parentheses.")
   (let*
       ((get-notes (lambda (ev-chord)
		     (filter
		      (lambda (m) (eq? 'NoteEvent (ly:music-property m 'name)))
		      (ly:music-property ev-chord 'elements))))
	(sec-note-events (get-notes secondary-note))
	(trill-events (filter (lambda (m) (music-has-type m 'trill-span-event))
			      (ly:music-property main-note 'elements))))

     (if (pair? sec-note-events)
	 (begin
	   (let*
	       ((trill-pitch (ly:music-property (car sec-note-events) 'pitch))
		(forced (ly:music-property (car sec-note-events ) 'force-accidental)))

	     (if (ly:pitch? trill-pitch)
		 (for-each (lambda (m) (ly:music-set-property! m 'pitch trill-pitch))
			   trill-events)
		 (begin
		   (ly:warning (_ "Second argument of \\pitchedTrill should be single note: "))
		   (display sec-note-events)))

	     (if (eq? forced #t)
		 (for-each (lambda (m) (ly:music-set-property! m 'force-accidental forced))
			   trill-events)))))
     main-note))



quoteDuring =
#(define-music-function
   (parser location what main-music)
   (string? ly:music?)
   (_i "Indicate a section of music to be quoted.  @var{what} indicates the name
of the quoted voice, as specified in an @code{\\addQuote} command.
@var{main-music} is used to indicate the length of music to be quoted;
usually contains spacers or multi-measure rests.")
  (make-music 'QuoteMusic
	      'element main-music
	      'quoted-music-name what
	      'origin location))



removeWithTag =
#(define-music-function
  (parser location tag music) (symbol? ly:music?)
  (_i "Remove elements of @var{music} that are tagged with @var{tag}.")
  (music-filter
   (lambda (m)
    (let* ((tags (ly:music-property m 'tags))
	   (res (memq tag tags)))
     (not res)))
 music))

resetRelativeOctave =
#(define-music-function
    (parser location reference-note)
    (ly:music?)
    (_i "Set the octave inside a \\relative section.")

   (let*
    ((notes (ly:music-property reference-note 'elements))
     (pitch (ly:music-property (car notes) 'pitch)))

    (set! (ly:music-property reference-note 'elements) '())
    (set! (ly:music-property reference-note
       'to-relative-callback)
       (lambda (music last-pitch)
	pitch))

    reference-note))

revertBeamSettings =
#(define-music-function
    (parser location
     context time-signature rule-type)
    (symbol? pair? symbol?)

 (_i "Revert beam settings in @var{context} for time signatures of
@var{time-signature} and groups of type
@var{group-type}.  @var{group-type} can be @code{end}
or @code{subdivide}.")
#{
  #(revert-beam-setting $time-signature $rule-type $context)
#})

rightHandFinger =
#(define-music-function (parser location finger) (number-or-string?)
   (_i "Apply @var{finger} as a fingering indication.")

   (apply make-music
	  (append
	   (list
	    'StrokeFingerEvent
	    'origin location)
	   (if	(string? finger)
		(list 'text finger)
		(list 'digit finger)))))



scaleDurations =
#(define-music-function (parser location fraction music) (number-pair? ly:music?)
   (_i "Multiply the duration of events in @var{music} by @var{fraction}.")
   (ly:music-compress music
		      (ly:make-moment (car fraction) (cdr fraction))))

setBeatGrouping =
#(define-music-function (parser location grouping) (pair?)
   (_i "Set the beat grouping in the current time signature to
@var{grouping}.")
   (define (default-group-setting c)
    (let* ((context-time-signature
	    (ly:context-property c 'timeSignatureFraction))
	   (time-signature (if (null? context-time-signature)
			       '(4 . 4)
			       context-time-signature)))
      (override-property-setting
       c
       'beamSettings
       (list time-signature 'end)
       (list  (cons '* grouping)))))

   (context-spec-music
     (make-apply-context default-group-setting)
     'Score))

shiftDurations =
#(define-music-function (parser location dur dots arg) (integer? integer? ly:music?)
   (_i "Scale @var{arg} up by a factor of @var{2^dur*(2-(1/2)^dots)}.")

   (music-map
    (lambda (x)
      (shift-one-duration-log x dur dots)) arg))

spacingTweaks =
#(define-music-function (parser location parameters) (list?)
   (_i "Set the system stretch, by reading the 'system-stretch property of
the `parameters' assoc list.")
   #{
      \overrideProperty #"Score.NonMusicalPaperColumn"
	#'line-break-system-details
	#$(list (cons 'alignment-extra-space (cdr (assoc 'system-stretch parameters)))
		(cons 'system-Y-extent (cdr (assoc 'system-Y-extent parameters))))
   #})

styledNoteHeads =
#(define-music-function
   (parser location style heads music)
   (symbol? list-or-symbol? ly:music?)
   (_i "Set @var{heads} in @var{music} to @var{style}.")
   (style-note-heads heads style music))



tag =
#(define-music-function (parser location tag arg)
   (symbol? ly:music?)

   (_i "Add @var{tag} to the @code{tags} property of @var{arg}.")

   (set!
    (ly:music-property arg 'tags)
    (cons tag
	  (ly:music-property arg 'tags)))
   arg)

transposedCueDuring =
#(define-music-function
  (parser location what dir pitch-note main-music)
  (string? ly:dir? ly:music? ly:music?)

  (_i "Insert notes from the part @var{what} into a voice called @code{cue},
using the transposition defined by @var{pitch-note}.  This happens
simultaneously with @var{main-music}, which is usually a rest.	The
argument @var{dir} determines whether the cue notes should be notated
as a first or second voice.")

  (make-music 'QuoteMusic
	      'element main-music
	      'quoted-context-type 'Voice
	      'quoted-context-id "cue"
	      'quoted-music-name what
	      'quoted-voice-direction dir
	      'quoted-transposition (pitch-of-note pitch-note)
	      'origin location))

transposition =
#(define-music-function (parser location pitch-note) (ly:music?)
   (_i "Set instrument transposition")

   (context-spec-music
    (make-property-set 'instrumentTransposition
		       (ly:pitch-negate (pitch-of-note pitch-note)))
	'Staff))

tweak =
#(define-music-function (parser location sym val arg)
   (symbol? scheme? ly:music?)
   (_i "Add @code{sym . val} to the @code{tweaks} property of @var{arg}.")

   (if (equal? (object-property sym 'backend-type?) #f)
       (begin
	 (ly:warning (_ "cannot find property type-check for ~a") sym)
	 (ly:warning (_ "doing assignment anyway"))))
   (set!
    (ly:music-property arg 'tweaks)
    (acons sym val
	   (ly:music-property arg 'tweaks)))
   arg)



unfoldRepeats =
#(define-music-function (parser location music) (ly:music?)
   (_i "Force any @code{\\repeat volta}, @code{\\repeat tremolo} or
@code{\\repeat percent} commands in @var{music} to be interpreted
as @code{\\repeat unfold}.")
   (unfold-repeats music))



withMusicProperty =
#(define-music-function (parser location sym val music) (symbol? scheme? ly:music?)
   (_i "Set @var{sym} to @var{val} in @var{music}.")

   (set! (ly:music-property music sym) val)
   music)
