X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=ly%2Fmusic-functions-init.ly;h=2dded22e3d77acd2b2dbcab500d6a01a5f893be9;hb=cfc4cbf34569db6a6c8968694f86e36b206a9d05;hp=e914b70326435296f9968343badc6d16fa7f3b78;hpb=87eedcd59f4082cb0841528ad5bc82cb1d1191e3;p=lilypond.git

diff --git a/ly/music-functions-init.ly b/ly/music-functions-init.ly
index e914b70326..2dded22e3d 100644
--- a/ly/music-functions-init.ly
+++ b/ly/music-functions-init.ly
@@ -1,22 +1,24 @@
 % -*-Scheme-*-
 
-\version "2.10.0"
+\version "2.12.0"
 
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %% this file is alphabetically sorted.
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-%% need SRFI-1 filter 
+%% need SRFI-1 filter
 
 #(use-modules (srfi srfi-1))
 
 acciaccatura =
-#(def-grace-function startAcciaccaturaMusic stopAcciaccaturaMusic)
+#(def-grace-function startAcciaccaturaMusic stopAcciaccaturaMusic
+   (_i "Create an acciaccatura from the following music expression"))
 
 addQuote =
 #(define-music-function (parser location name music) (string? ly:music?)
-   (_i "Add a piece of music to be quoted ")
+   (_i "Define @var{music} as a quotable music expression named
+@var{name}")
    (add-quotable parser name music)
    (make-music 'SequentialMusic 'void #t))
 
@@ -27,11 +29,11 @@ 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
@@ -50,34 +52,38 @@ afterGrace =
 
 applyMusic =
 #(define-music-function (parser location func music) (procedure? ly:music?)
-               (func music))
+   (_i"Apply procedure @var{func} to @var{music}.")
+  (func music))
 
 
 applyOutput =
 #(define-music-function (parser location ctx proc) (symbol? procedure?)
-                (make-music 'ApplyOutputEvent
-                  'origin location
-                  'procedure proc
-                  'context-type ctx))
+  (_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)
-
+#(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
@@ -89,35 +95,40 @@ assertBeamSlope =
 
 autochange =
 #(define-music-function (parser location music) (ly:music?)
-               (make-autochange-music parser music))
+  (_i "Make voices that switch between staves automatically")
+  (make-autochange-music parser music))
 
 applyContext =
 #(define-music-function (parser location proc) (procedure?)
-                 (make-music 'ApplyContext 
-                   'origin location
-                   'procedure proc))
+  (_i "Modify context properties with Scheme procedure @var{proc}.")
+  (make-music 'ApplyContext
+              'origin location
+              'procedure proc))
 
 
-balloonText =
-#(define-music-function (parser location offset text) (number-pair? markup?)
-   
+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))
 
-balloonGrobText =
-#(define-music-function (parser location grob-name offset text) (symbol? number-pair? markup?)
-   
+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
-		'symbol grob-name
 		'X-offset (car offset)
 		'Y-offset (cdr offset)
 		'text text))
 
+
 bar =
-#(define-music-function (parser location type)
-   (string?)
+#(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))
@@ -125,9 +136,10 @@ bar =
 
 barNumberCheck =
 #(define-music-function (parser location n) (integer?)
-   (make-music 'ApplyContext 
+  (_i "Print a warning if the current bar number is not @var{n}.")
+   (make-music 'ApplyContext
 	       'origin location
-	       'procedure 
+	       'procedure
 	       (lambda (c)
 		 (let*
 		     ((cbn (ly:context-property c 'currentBarNumber)))
@@ -136,70 +148,90 @@ barNumberCheck =
 					 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) ()
-            (make-music 'EventChord 
+  (_i "Insert a breath mark.")
+            (make-music 'EventChord
               'origin location
               'elements (list (make-music 'BreathingEvent))))
 
-bendAfter =
-#(define-music-function (parser location delta) (integer?)
-	      
-  (make-music 'BendAfterEvent
-   'delta-step delta))
 
 clef =
-#(define-music-function (parser location type)
-   (string?)
-   (_i "Set the current clef.")
-
+#(define-music-function (parser location type) (string?)
+  (_i "Set the current clef to @var{type}.")
    (make-clef-set type))
 
 
-compressMusic =
-#(define-music-function
-		  (parser location fraction music) (number-pair? ly:music?)
-		  (ly:music-compress music (ly:make-moment (car fraction) (cdr fraction))))
-
-
-cueDuring = 
+cueDuring =
 #(define-music-function
-  (parser location what dir main-music)
-  (string? ly:dir? ly:music?)
+  (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 
+	      'element main-music
 	      'quoted-context-type 'Voice
 	      'quoted-context-id "cue"
 	      'quoted-music-name what
 	      'quoted-voice-direction dir
 	      'origin location))
 
-%% The following causes an error with guile 1.6.8 (guile 1.6.7 and 1.8.x are fine)
-#(use-modules (scm display-lily))
-
 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 "Rearrange durations in ARGUMENT so there is an
-acceleration/deceleration. ")
-   
+ (_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 
+     (music-map
       (lambda (mus)
 	(if (and (eq? (ly:music-property mus 'name) 'EventChord)
 		 (< 0 (ly:moment-main-denominator (ly:music-length mus))))
@@ -217,15 +249,15 @@ acceleration/deceleration. ")
      argument))
 
 grace =
-#(def-grace-function startGraceMusic stopGraceMusic)
-
+#(def-grace-function startGraceMusic stopGraceMusic
+   (_i "Insert @var{music} as grace notes."))
 
 "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))
@@ -234,6 +266,8 @@ addInstrumentDefinition =
 instrumentSwitch =
 #(define-music-function
    (parser location name) (string?)
+   (_i "Switch instrument to @var{name}, which must be predefined with
+@var{\addInstrumentDefinition}.")
    (let*
        ((handle  (assoc name instrument-definitions))
 	(instrument-def (if handle (cdr handle) '()))
@@ -252,9 +286,29 @@ instrumentSwitch =
       'Staff)))
 
 
+%% Parser used to read page-layout file, and then retreive score tweaks.
+#(define page-layout-parser #f)
+
+includePageLayoutFile =
+#(define-music-function (parser location) ()
+   (_i "Include the file @var{<basename>-page-layout.ly}. Deprecated as
+part of two-pass spacing.")
+   (if (not (ly:get-option 'dump-tweaks))
+       (let ((tweak-filename (format #f "~a-page-layout.ly"
+				     (ly:parser-output-name parser))))
+	 (if (access? tweak-filename R_OK)
+	     (begin
+	       (ly:message "Including tweak file ~a" tweak-filename)
+               (set! page-layout-parser (ly:parser-clone parser))
+	       (ly:parser-parse-string page-layout-parser
+                                       (format #f "\\include \"~a\""
+                                               tweak-filename))))))
+   (make-music 'SequentialMusic 'void #t))
+
 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))
@@ -264,22 +318,41 @@ keepWithTag =
       res)))
    music))
 
-
+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))
 
 killCues =
 #(define-music-function
    (parser location music)
    (ly:music?)
+   (_i "Remove cue notes from @var{music}.")
    (music-map
     (lambda (mus)
       (if (string? (ly:music-property mus 'quoted-music-name))
 	  (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 =
@@ -287,20 +360,10 @@ musicMap =
 	     (music-map proc mus))
 
 
-
-oldaddlyrics =
-#(define-music-function (parser location music lyrics) (ly:music? ly:music?)
-
-              (make-music 'OldLyricCombineMusic 
-                          'origin location
-                          'elements (list music lyrics)))
-
-
 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\"}")
@@ -326,35 +389,89 @@ or @code{\"GrobName\"}")
 			grob-name)
 		       (set! (ly:grob-property grob property) value))))))
 
-
-removeWithTag = 
-#(define-music-function
-  (parser location tag music) (symbol? ly:music?)
-  (music-filter
-   (lambda (m)
-    (let* ((tags (ly:music-property m 'tags))
-           (res (memq tag tags)))
-     (not res)))
- music))
+%% These 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 (ie 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))))
+
+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 '()))))
+
+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))))
+
+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 '()))))
+
+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))))
 
 %% Todo:
 %% doing
 %% define-music-function in a .scm causes crash.
 
-octave =
+octaveCheck =
 #(define-music-function (parser location pitch-note) (ly:music?)
    (_i "octave check")
 
    (make-music 'RelativeOctaveCheck
 	       'origin location
-	       'pitch (pitch-of-note pitch-note) 
-	       ))
+	       'pitch (pitch-of-note pitch-note)
+           ))
+
+ottava = #(define-music-function (parser location octave) (number?)
+  (_i "set the octavation ")
+  (make-ottava-set octave))
+
 partcombine =
 #(define-music-function (parser location part1 part2) (ly:music? ly:music?)
                 (make-part-combine-music parser
 					 (list part1 part2)))
 
-	      
+
 pitchedTrill =
 #(define-music-function
    (parser location main-note secondary-note)
@@ -365,29 +482,28 @@ pitchedTrill =
 		      (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) (memq 'trill-span-event (ly:music-property m 'types)))
-			      (ly:music-property main-note 'elements)))
-
-	(trill-pitch
-	 (if (pair? sec-note-events)
-	     (ly:music-property (car sec-note-events) 'pitch)
-	     )))
-     
-     (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)))
+	(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))
-   
-parenthesize =
-#(define-music-function (parser loc arg) (ly:music?)
-   (_i "Tag @var{arg} to be parenthesized.")
 
-   (set! (ly:music-property arg 'parenthesize) #t)
-   arg)
+
 
 %% for lambda*
 #(use-modules (ice-9 optargs))
@@ -425,7 +541,7 @@ Example:
     (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 
+      (list-set! current-voices 0 (cons (make-music 'SequentialMusic
                                          'elements (reverse! current-sequence))
                                         (car current-voices)))
       (set! current-sequence (list))
@@ -439,7 +555,7 @@ Example:
             ((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 
+                      (let ((origins (remove not (map music-origin
                                                       (ly:music-property music 'elements)))))
                         (and (not (null? origins)) (car origins)))))))
     ;;
@@ -468,15 +584,15 @@ Example:
                       (let ((moment-reference (ly:music-length (car seqs))))
                         (for-each (lambda (seq moment)
                                     (if (not (equal? moment moment-reference))
-                                        (ly:music-message seq 
+                                        (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 
+          (ly:parser-define! parser voice-id
+                             (make-music 'SequentialMusic
                                'origin location
                                'elements voice)))
         voice-ids voices))
@@ -485,6 +601,23 @@ Example:
 
 
 
+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)
+
+
 quoteDuring = #
 (define-music-function
   (parser location what main-music)
@@ -515,11 +648,18 @@ resetRelativeOctave  =
     reference-note))
 
 
+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))))
+
+
 
 shiftDurations =
 #(define-music-function (parser location dur dots arg) (integer? integer? ly:music?)
-   (_i "")
-   
+   (_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))
@@ -535,33 +675,14 @@ the `parameters' assoc list.")
 		(cons 'system-Y-extent (cdr (assoc 'system-Y-extent parameters))))
    #})
 
-%% Parser used to read page-layout file, and then retreive score tweaks.
-#(define page-layout-parser #f)
-
-includePageLayoutFile = 
-#(define-music-function (parser location) ()
-   (_i "If page breaks and tweak dump is not asked, and the file
-<basename>-page-layout.ly exists, include it.")
-   (if (not (ly:get-option 'dump-tweaks))
-       (let ((tweak-filename (format #f "~a-page-layout.ly"
-				     (ly:parser-output-name parser))))
-	 (if (access? tweak-filename R_OK)
-	     (begin
-	       (ly:message "Including tweak file ~a" tweak-filename)
-               (set! page-layout-parser (ly:parser-clone parser))
-	       (ly:parser-parse-string page-layout-parser
-                                       (format #f "\\include \"~a\""
-                                               tweak-filename))))))
-   (make-music 'SequentialMusic 'void #t))
-
 
 rightHandFinger =
 #(define-music-function (parser location finger) (number-or-string?)
-   (_i "Define a StrokeFingerEvent")
-   
+   (_i "Apply @var{finger} as a fingering indication.")
+
    (apply make-music
 	  (append
-	   (list 
+	   (list
 	    'StrokeFingerEvent
 	    'origin location)
 	   (if  (string? finger)
@@ -579,6 +700,21 @@ scoreTweak =
              (make-music 'SequentialMusic)))
        (make-music 'SequentialMusic)))
 
+
+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)
@@ -610,29 +746,23 @@ transposition =
 		       (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}.")
-	   
-	   (set!
-	    (ly:music-property arg 'tweaks)
-	    (acons sym val
-		   (ly:music-property arg 'tweaks)))
-	   arg)
-
-tag = #(define-music-function (parser location tag arg)
-   (symbol? ly:music?)
-
-   (_i "Add @var{tag} to the @code{tags} property of @var{arg}.")
+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 'tags)
-    (cons tag
-	  (ly:music-property arg 'tags)))
+    (ly:music-property arg 'tweaks)
+    (acons sym val
+	   (ly:music-property arg 'tweaks)))
    arg)
 
 
+
 unfoldRepeats =
 #(define-music-function (parser location music) (ly:music?)
 		  (unfold-repeats music))
@@ -645,5 +775,3 @@ withMusicProperty =
 
    (set! (ly:music-property music sym) val)
    music)
-
-