X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=scm%2Fmusic-functions.scm;h=31b6c8ad3c48d3861b3ffe500b8a1c6d2f627d76;hb=1edd073d300fee9f1280e020227bb5820f37bc20;hp=b3d58db60a916f7753fa9f2ee9542ed5da0824a8;hpb=7461c479c7a2e448b2d1da9759246b0cc1c9257a;p=lilypond.git diff --git a/scm/music-functions.scm b/scm/music-functions.scm index b3d58db60a..31b6c8ad3c 100644 --- a/scm/music-functions.scm +++ b/scm/music-functions.scm @@ -1,9 +1,20 @@ -;;;; music-functions.scm -- +;;;; This file is part of LilyPond, the GNU music typesetter. ;;;; -;;;; source file of the GNU LilyPond music typesetter -;;;; -;;;; (c) 1998--2009 Jan Nieuwenhuizen +;;;; Copyright (C) 1998--2011 Jan Nieuwenhuizen ;;;; Han-Wen Nienhuys +;;;; +;;;; LilyPond is free software: you can redistribute it and/or modify +;;;; it under the terms of the GNU General Public License as published by +;;;; the Free Software Foundation, either version 3 of the License, or +;;;; (at your option) any later version. +;;;; +;;;; LilyPond is distributed in the hope that it will be useful, +;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +;;;; GNU General Public License for more details. +;;;; +;;;; You should have received a copy of the GNU General Public License +;;;; along with LilyPond. If not, see . ;; (use-modules (ice-9 optargs)) @@ -25,15 +36,27 @@ (make-procedure-with-setter ly:grob-property ly:grob-set-property!)) +(define-public ly:grob-object + (make-procedure-with-setter ly:grob-object + ly:grob-set-object!)) + +(define-public ly:grob-parent + (make-procedure-with-setter ly:grob-parent + ly:grob-set-parent!)) + (define-public ly:prob-property (make-procedure-with-setter ly:prob-property ly:prob-set-property!)) +(define-public ly:context-property + (make-procedure-with-setter ly:context-property + ly:context-set-property!)) + (define-public (music-map function music) "Apply @var{function} to @var{music} and all of the music it contains. -First it recurses over the children, then the function is applied to MUSIC. -" +First it recurses over the children, then the function is applied to +@var{music}." (let ((es (ly:music-property music 'elements)) (e (ly:music-property music 'element))) (set! (ly:music-property music 'elements) @@ -44,7 +67,7 @@ First it recurses over the children, then the function is applied to MUSIC. (function music))) (define-public (music-filter pred? music) - "Filter out music expressions that do not satisfy PRED." + "Filter out music expressions that do not satisfy @var{pred?}." (define (inner-music-filter pred? music) "Recursive function." @@ -73,7 +96,8 @@ First it recurses over the children, then the function is applied to MUSIC. (make-music 'Music))) ;must return music. (define-public (display-music music) - "Display music, not done with music-map for clarity of presentation." + "Display music, not done with @code{music-map} for clarity of +presentation." (display music) (display ": { ") @@ -111,7 +135,7 @@ For instance, ((and (not (string? arg)) (markup? arg)) ;; a markup (inner-markup->make-markup arg)) (else ;; scheme arg - arg))) + (music->make-music arg)))) (define (inner-markup->make-markup mrkup) (if (string? mrkup) `(#:simple ,mrkup) @@ -124,8 +148,9 @@ For instance, `(markup ,@(inner-markup->make-markup markup-expression)))) (define-public (music->make-music obj) - "Generate a expression that, once evaluated, may return an object equivalent to `obj', -that is, for a music expression, a (make-music ...) form." + "Generate an expression that, once evaluated, may return an object +equivalent to @var{obj}, that is, for a music expression, a +@code{(make-music ...)} form." (cond (;; markup expression (markup? obj) (markup-expression->make-markup obj)) @@ -204,9 +229,9 @@ Returns `obj'. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (define-public (shift-one-duration-log music shift dot) - " add SHIFT to duration-log of 'duration in music and optionally - a dot to any note encountered. This scales the music up by a factor - 2^shift * (2 - (1/2)^dot)" + "Add @var{shift} to @code{duration-log} of @code{'duration} in +@var{music} and optionally @var{dot} to any note encountered. This +scales the music up by a factor `2^@var{shift} * (2 - (1/2)^@var{dot})'." (let ((d (ly:music-property music 'duration))) (if (ly:duration? d) (let* ((cp (ly:duration-factor d)) @@ -222,7 +247,8 @@ Returns `obj'. music)) (define-public (make-repeat name times main alts) - "create a repeat music expression, with all properties initialized properly" + "Create a repeat music expression, with all properties initialized +properly." (define (first-note-duration music) "Finds the duration of the first NoteEvent by searching depth-first through MUSIC." @@ -246,9 +272,20 @@ through MUSIC." (set! (ly:music-property r 'element) main) (set! (ly:music-property r 'repeat-count) (max times 1)) (set! (ly:music-property r 'elements) talts) - (if (equal? name "tremolo") - (let* ((dots (1- (logcount times))) - (mult (/ (* times (ash 1 dots)) (1- (ash 2 dots)))) + (if (and (equal? name "tremolo") + (or (pair? (ly:music-property main 'elements)) + (ly:music? (ly:music-property main 'element)))) + ;; This works for single-note and multi-note tremolos! + (let* ((children (if (music-is-of-type? main 'sequential-music) + ;; \repeat tremolo n { ... } + (length (ly:music-property main 'elements)) + ;; \repeat tremolo n c4 + 1)) + ;; # of dots is equal to the 1 in bitwise representation (minus 1)! + (dots (1- (logcount (* times children)))) + ;; The remaining missing multiplicator to scale the notes by + ;; times * children + (mult (/ (* times children (ash 1 dots)) (1- (ash 2 dots)))) (shift (- (ly:intlog2 (floor mult)))) (note-duration (first-note-duration r)) (duration-log (if (ly:duration? note-duration) @@ -258,27 +295,31 @@ through MUSIC." (set! (ly:music-property r 'tremolo-type) tremolo-type) (if (not (integer? mult)) (ly:warning (_ "invalid tremolo repeat count: ~a") times)) - (if (memq 'sequential-music (ly:music-property main 'types)) - ;; \repeat "tremolo" { c4 d4 } - (let ((children (length (ly:music-property main 'elements)))) - - ;; fixme: should be more generic. - (if (and (not (= children 2)) - (not (= children 1))) - (ly:warning (_ "expecting 2 elements for chord tremolo, found ~a") children)) - (ly:music-compress r (ly:make-moment 1 children)) - (shift-duration-log r - (if (= children 2) (1- shift) shift) - dots)) - ;; \repeat "tremolo" c4 - (shift-duration-log r shift dots))) + ;; Adjust the time of the notes + (ly:music-compress r (ly:make-moment 1 children)) + ;; Adjust the displayed note durations + (shift-duration-log r shift dots)) r))) +(define (calc-repeat-slash-count music) + "Given the child-list @var{music} in @code{PercentRepeatMusic}, +calculate the number of slashes based on the durations. Returns @code{0} +if durations in in @var{music} vary, allowing slash beats and double-percent +beats to be distinguished." + (let* ((durs (map (lambda (elt) + (duration-of-note elt)) + (extract-named-music music 'EventChord))) + (first-dur (car durs))) + + (if (every (lambda (d) (equal? d first-dur)) durs) + (max (- (ly:duration-log first-dur) 2) 1) + 0))) + ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;; clusters. (define-public (note-to-cluster music) - "Replace NoteEvents by ClusterNoteEvents." + "Replace @code{NoteEvents} by @code{ClusterNoteEvents}." (if (eq? (ly:music-property music 'name) 'NoteEvent) (make-music 'ClusterNoteEvent 'pitch (ly:music-property music 'pitch) @@ -292,38 +333,37 @@ through MUSIC." ;; repeats. (define-public (unfold-repeats music) - " -This function replaces all repeats with unfold repeats. " + "Replace all repeats with unfolded repeats." (let ((es (ly:music-property music 'elements)) - (e (ly:music-property music 'element)) - ) - (if (memq 'repeated-music (ly:music-property music 'types)) - (let* - ((props (ly:music-mutable-properties music)) - (old-name (ly:music-property music 'name)) - (flattened (flatten-alist props))) + (e (ly:music-property music 'element))) + (if (memq 'repeated-music (ly:music-property music 'types)) + (let* ((props (ly:music-mutable-properties music)) + (old-name (ly:music-property music 'name)) + (flattened (flatten-alist props))) (set! music (apply make-music (cons 'UnfoldedRepeatedMusic flattened))) (if (equal? old-name 'TremoloRepeatedMusic) (let* ((seq-arg? (memq 'sequential-music (ly:music-property e 'types))) - (count (ly:music-property music 'repeat-count)) + (count (ly:music-property music 'repeat-count)) (dot-shift (if (= 0 (remainder count 3)) - -1 0))) + -1 0)) + (child-count (if seq-arg? + (length (ly:music-property e 'elements)) + 0))) (if (= 0 -1) (set! count (* 2 (quotient count 3)))) - (shift-duration-log music (+ (if seq-arg? 1 0) + (shift-duration-log music (+ (if (= 2 child-count) + 1 0) (ly:intlog2 count)) dot-shift) (if seq-arg? - (ly:music-compress e (ly:make-moment (length (ly:music-property - e 'elements)) 1))))))) - + (ly:music-compress e (ly:make-moment child-count 1))))))) (if (pair? es) (set! (ly:music-property music 'elements) @@ -337,8 +377,8 @@ This function replaces all repeats with unfold repeats. " ;; property setting music objs. (define-public (make-grob-property-set grob gprop val) - "Make a Music expression that sets GPROP to VAL in GROB. Does a pop first, -i.e. this is not an override" + "Make a @code{Music} expression that sets @var{gprop} to @var{val} in +@var{grob}. Does a pop first, i.e., this is not an override." (make-music 'OverrideProperty 'symbol grob 'grob-property gprop @@ -346,14 +386,15 @@ i.e. this is not an override" 'pop-first #t)) (define-public (make-grob-property-override grob gprop val) - "Make a Music expression that overrides GPROP to VAL in GROB." + "Make a @code{Music} expression that overrides @var{gprop} to @var{val} +in @var{grob}." (make-music 'OverrideProperty 'symbol grob 'grob-property gprop 'grob-value val)) (define-public (make-grob-property-revert grob gprop) - "Revert the grob property GPROP for GROB." + "Revert the grob property @var{gprop} for @var{grob}." (make-music 'RevertProperty 'symbol grob 'grob-property gprop)) @@ -383,11 +424,11 @@ i.e. this is not an override" ;; TODO: take this from voicedGraceSettings or similar. '((Voice Stem font-size -3) (Voice NoteHead font-size -3) - (Voice TabNoteHead font-size -4) + (Voice TabNoteHead font-size -4) (Voice Dots font-size -3) (Voice Stem length-fraction 0.8) (Voice Stem no-stem-extend #t) - (Voice Beam thickness 0.384) + (Voice Beam beam-thickness 0.384) (Voice Beam length-fraction 0.8) (Voice Accidental font-size -4) (Voice AccidentalCautionary font-size -4) @@ -409,7 +450,7 @@ i.e. this is not an override" (define-safe-public (context-spec-music m context #:optional id) - "Add \\context CONTEXT = ID to M. " + "Add \\context CONTEXT = ID to M." (let ((cm (make-music 'ContextSpeccedMusic 'element m 'context-type context))) @@ -418,7 +459,7 @@ i.e. this is not an override" cm)) (define-public (descend-to-context m context) - "Like context-spec-music, but only descending. " + "Like @code{context-spec-music}, but only descending." (let ((cm (context-spec-music m context))) (ly:music-set-property! cm 'descend-only #t) cm)) @@ -468,87 +509,23 @@ i.e. this is not an override" (make-music 'PropertyUnset 'symbol sym)) -(define-public (make-ottava-set octavation) - (let ((m (make-music 'ApplyContext))) - (define (ottava-modify context) - "Either reset middleCPosition to the stored original, or remember -old middleCPosition, add OCTAVATION to middleCPosition, and set -OTTAVATION to `8va', or whatever appropriate." - (if (number? (ly:context-property context 'middleCOffset)) - (let ((where (ly:context-property-where-defined context 'middleCOffset))) - (ly:context-unset-property where 'middleCOffset) - (ly:context-unset-property where 'ottavation))) - - (let* ((offset (* -7 octavation)) - (string (cdr (assoc octavation '((2 . "15ma") - (1 . "8va") - (0 . #f) - (-1 . "8vb") - (-2 . "15mb")))))) - (ly:context-set-property! context 'middleCOffset offset) - (ly:context-set-property! context 'ottavation string) - (ly:set-middle-C! context))) - (set! (ly:music-property m 'procedure) ottava-modify) - (context-spec-music m 'Staff))) - -(define-public (set-octavation ottavation) - (ly:export (make-ottava-set ottavation))) - ;;; Need to keep this definition for \time calls from parser (define-public (make-time-signature-set num den) - "Set properties for time signature NUM/DEN." - (make-beam-rule-time-signature-set num den '())) + "Set properties for time signature @var{num}/@var{den}." + (make-music 'TimeSignatureMusic + 'numerator num + 'denominator den + 'beat-structure '())) ;;; Used for calls that include beat-grouping setting (define-public (set-time-signature num den . rest) - "Set properties for time signature @var{num/den}. -If @var{rest} is present, it is used to make a default -@code{beamSetting} rule." - (ly:export (apply make-beam-rule-time-signature-set - (list num den rest)))) - -(define-public (make-beam-rule-time-signature-set num den rest) - "Implement settings for new time signature. Can be -called from either make-time-signature-set (used by \time -in parser) or set-time-signature (called from scheme code -included in .ly file." - - (define (make-default-beaming-rule context) - (override-property-setting - context - 'beamSettings - (list (cons num den) 'end) - (list (cons '* (car rest))))) - - (let* ((set1 (make-property-set 'timeSignatureFraction (cons num den))) - (beat (ly:make-moment 1 den)) - (len (ly:make-moment num den)) - (set2 (make-property-set 'beatLength beat)) - (set3 (make-property-set 'measureLength len)) - (beaming-rule - (if (null? rest) - '() - (list (make-apply-context make-default-beaming-rule)))) - (output (cons* set1 set2 set3 beaming-rule))) - (descend-to-context - (context-spec-music - (make-sequential-music output) - 'Timing) - 'Score))) - -(define-public (make-mark-set label) - "Make the music for the \\mark command." - (let* ((set (if (integer? label) - (context-spec-music (make-property-set 'rehearsalMark label) - 'Score) - #f)) - (ev (make-music 'MarkEvent)) - (ch (make-event-chord (list ev)))) - (if set - (make-sequential-music (list set ch)) - (begin - (set! (ly:music-property ev 'label) label) - ch)))) + "Set properties for time signature @var{num}/@var{den}. +If @var{rest} is present, it is used to set @code{beatStructure}." + (ly:export + (make-music 'TimeSignatureMusic + 'numerator num + 'denominator den + 'beat-structure (if (null? rest) rest (car rest))))) (define-safe-public (make-articulation name) (make-music 'ArticulationEvent @@ -599,14 +576,14 @@ inside of and outside of chord construct." (revert-head-style heads))))) (define-public (set-mus-properties! m alist) - "Set all of ALIST as properties of M." + "Set all of @var{alist} as properties of @var{m}." (if (pair? alist) (begin (set! (ly:music-property m (caar alist)) (cdar alist)) (set-mus-properties! m (cdr alist))))) (define-public (music-separator? m) - "Is M a separator?" + "Is @var{m} a separator?" (let ((ts (ly:music-property m 'types))) (memq 'separator ts))) @@ -614,10 +591,10 @@ inside of and outside of chord construct." (define (voicify-list lst number) "Make a list of Musics. - voicify-list :: [ [Music ] ] -> number -> [Music] - LST is a list music-lists. +voicify-list :: [ [Music ] ] -> number -> [Music] +LST is a list music-lists. - NUMBER is 0-base, i.e. Voice=1 (upstems) has number 0. +NUMBER is 0-base, i.e., Voice=1 (upstems) has number 0. " (if (null? lst) '() @@ -625,7 +602,7 @@ inside of and outside of chord construct." (make-sequential-music (list (make-voice-props-set number) (make-simultaneous-music (car lst)))) - 'Voice (number->string (1+ number))) + 'Bottom (number->string (1+ number))) (voicify-list (cdr lst) (1+ number))))) (define (voicify-chord ch) @@ -636,7 +613,7 @@ inside of and outside of chord construct." ch)) (define-public (voicify-music m) - "Recursively split chords that are separated with \\ " + "Recursively split chords that are separated with @code{\\\\}." (if (not (ly:music? m)) (ly:error (_ "music expected: ~S") m)) (let ((es (ly:music-property m 'elements)) @@ -657,7 +634,7 @@ inside of and outside of chord construct." ;; Make a function that checks score element for being of a specific type. (define-public (make-type-checker symbol) (lambda (elt) - (not (eq? #f (memq symbol (ly:grob-property elt 'interfaces)))))) + (grob::has-interface elt symbol))) (define-public ((outputproperty-compatibility func sym val) grob g-context ao-context) (if (func grob) @@ -665,25 +642,20 @@ inside of and outside of chord construct." (define-public ((set-output-property grob-name symbol val) grob grob-c context) - "Usage: - -\\applyoutput #(set-output-property 'Clef 'extra-offset '(0 . 1)) - -" + "Usage example: +@code{\\applyoutput #(set-output-property 'Clef 'extra-offset '(0 . 1))}" (let ((meta (ly:grob-property grob 'meta))) - (if (equal? (cdr (assoc 'name meta)) grob-name) + (if (equal? (assoc-get 'name meta) grob-name) (set! (ly:grob-property grob symbol) val)))) ;; (define-public (smart-bar-check n) - "Make a bar check that checks for a specific bar number. -" + "Make a bar check that checks for a specific bar number." (let ((m (make-music 'ApplyContext))) (define (checker tr) (let* ((bn (ly:context-property tr 'currentBarNumber))) - (if (= bn n) - #t + (or (= bn n) (ly:error ;; FIXME: uncomprehensable message (_ "Bar check failed. Expect to be at ~a, instead at ~a") @@ -693,9 +665,8 @@ inside of and outside of chord construct." (define-public (skip->rest mus) - - "Replace MUS by RestEvent of the same duration if it is a -SkipEvent. Useful for extracting parts from crowded scores" + "Replace @var{mus} by @code{RestEvent} of the same duration if it is a +@code{SkipEvent}. Useful for extracting parts from crowded scores." (if (memq (ly:music-property mus 'name) '(SkipEvent SkipMusic)) (make-music 'RestEvent 'duration (ly:music-property mus 'duration)) @@ -741,20 +712,20 @@ SkipEvent. Useful for extracting parts from crowded scores" nv)) (define (vector-map f v) - "Map F over V. This function returns nothing." + "Map F over V. This function returns nothing." (do ((n (vector-length v)) (i 0 (+ i 1))) ((>= i n)) (f (vector-ref v i)))) (define (vector-reverse-map f v) - "Map F over V, N to 0 order. This function returns nothing." + "Map F over V, N to 0 order. This function returns nothing." (do ((i (- (vector-length v) 1) (- i 1))) ((< i 0)) (f (vector-ref v i)))) (define-public (add-grace-property context-name grob sym val) - "Set SYM=VAL for GROB in CONTEXT-NAME. " + "Set @var{sym}=@var{val} for @var{grob} in @var{context-name}." (define (set-prop context) (let* ((where (ly:context-property-where-defined context 'graceSettings)) (current (ly:context-property where 'graceSettings)) @@ -764,7 +735,7 @@ SkipEvent. Useful for extracting parts from crowded scores" (ly:export (context-spec-music (make-apply-context set-prop) 'Voice))) (define-public (remove-grace-property context-name grob sym) - "Remove all SYM for GROB in CONTEXT-NAME. " + "Remove all @var{sym} for @var{grob} in @var{context-name}." (define (sym-grob-context? property sym grob context-name) (and (eq? (car property) context-name) (eq? (cadr property) grob) @@ -818,10 +789,11 @@ Syntax: ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (define-public (cue-substitute quote-music) - "Must happen after quote-substitute." + "Must happen after @code{quote-substitute}." (if (vector? (ly:music-property quote-music 'quoted-events)) (let* ((dir (ly:music-property quote-music 'quoted-voice-direction)) + (clef (ly:music-property quote-music 'quoted-music-clef)) (main-voice (if (eq? 1 dir) 1 0)) (cue-voice (if (eq? 1 dir) 0 1)) (main-music (ly:music-property quote-music 'element)) @@ -833,14 +805,19 @@ Syntax: ;; to have opposite stems. (begin (set! return-value - ;; cannot context-spec Quote-music, since context ;; for the quotes is determined in the iterator. (make-sequential-music (list + (if (null? clef) + (make-music 'Music) + (make-cue-clef-set clef)) (context-spec-music (make-voice-props-set cue-voice) 'CueVoice "cue") quote-music - (context-spec-music (make-voice-props-revert) 'CueVoice "cue")))) + (context-spec-music (make-voice-props-revert) 'CueVoice "cue") + (if (null? clef) + (make-music 'Music) + (make-cue-clef-unset))))) (set! main-music (make-sequential-music (list @@ -854,9 +831,8 @@ Syntax: (define-public ((quote-substitute quote-tab) music) (let* ((quoted-name (ly:music-property music 'quoted-music-name)) - (quoted-vector (if (string? quoted-name) - (hash-ref quote-tab quoted-name #f) - #f))) + (quoted-vector (and (string? quoted-name) + (hash-ref quote-tab quoted-name #f)))) (if (string? quoted-name) @@ -899,37 +875,26 @@ Syntax: music) (define-public (make-duration-of-length moment) - "Make duration of the given MOMENT length." + "Make duration of the given @code{moment} length." (ly:make-duration 0 0 (ly:moment-main-numerator moment) (ly:moment-main-denominator moment))) -(define (skip-this moment) - "set skipTypesetting, make SkipMusic of the given MOMENT length, - and then unset skipTypesetting." +(define (make-skipped moment bool) + "Depending on BOOL, set or unset skipTypesetting, +then make SkipMusic of the given MOMENT length, and +then revert skipTypesetting." (make-sequential-music (list - (context-spec-music (make-property-set 'skipTypesetting #t) + (context-spec-music (make-property-set 'skipTypesetting bool) 'Score) (make-music 'SkipMusic 'duration (make-duration-of-length moment)) - (context-spec-music (make-property-set 'skipTypesetting #f) - 'Score)))) - -(define (unskip-this moment) - "unset skipTypesetting, make SkipMusic of the given MOMENT length, - and then set skipTypesetting." - (make-sequential-music - (list - (context-spec-music (make-property-set 'skipTypesetting #f) - 'Score) - (make-music 'SkipMusic 'duration - (make-duration-of-length moment)) - (context-spec-music (make-property-set 'skipTypesetting #t) + (context-spec-music (make-property-set 'skipTypesetting (not bool)) 'Score)))) (define (skip-as-needed music parser) - "Replace MUSIC by + "Replace MUSIC by << { \\set skipTypesetting = ##f LENGTHOF(\\showFirstLength) \\set skipTypesetting = ##t @@ -940,51 +905,54 @@ Syntax: When only showFirstLength is set, the 'length property of the music is overridden to speed up compiling." - (let* - ((show-last (ly:parser-lookup parser 'showLastLength)) - (show-first (ly:parser-lookup parser 'showFirstLength))) - (cond - - ;; both properties may be set. - ((and (ly:music? show-first) (ly:music? show-last)) - (let* - ((orig-length (ly:music-length music)) - (skip-length (ly:moment-sub orig-length (ly:music-length show-last))) - (begin-length (ly:music-length show-first))) - (make-simultaneous-music - (list - (make-sequential-music - (list - (skip-this skip-length) - ;; let's draw a separator between the beginning and the end - (context-spec-music (make-property-set 'whichBar "||") - 'Timing))) - (unskip-this begin-length) - music)))) - - ;; we may only want to print the last length - ((ly:music? show-last) - (let* - ((orig-length (ly:music-length music)) - (skip-length (ly:moment-sub orig-length (ly:music-length show-last)))) - (make-simultaneous-music - (list - (skip-this skip-length) - music)))) - - ;; we may only want to print the beginning; in this case - ;; only the first length will be processed (much faster). - ((ly:music? show-first) - (let* - ((orig-length (ly:music-length music)) - (begin-length (ly:music-length show-first))) - ;; the first length must not exceed the original length. - (if (ly:moment