\repeat unfold 8 {c8}
@end lilypond
-In a similar fashion, eighth notes in 3/4 time are beamed as a full
-measure by default. To beam eighth notes in 3/4 time on the beat,
-reset @code{beamExceptions}.
+In traditional engraving, eighth notes can have special beaming rules.
+A measure consisting of only eighth notes can be beamed in one. This rule is
+controlled by the context property @code{beamWholeMeasure}:
@lilypond[quote,verbatim,relative=2]
\time 3/4
-% by default we beam in (3) due to beamExceptions
-\repeat unfold 6 {a8} |
-% This will beam (1 1 1) due to beatLength
-\set Timing.beamExceptions = #'()
-\repeat unfold 6 {a8}
+% By default we beam in one
+\repeat unfold 6 { a8 }
+% We can avoid beaming in one
+\set Timing.beamWholeMeasure = ##f
+\repeat unfold 6 { a8 }
+@end lilypond
+
+In some engraving from the Romantic and Classical periods,
+a half-measure of eighth notes can be beamed
+together even though this violates the general rule (see Gould, p. 153).
+This behavior is controlled by the context property @code{beamHalfMeasure}:
+
+@lilypond[quote,verbatim,relative=2]
+\time 3/4
+% By default we avoid half-measure beams
+r4. a8 a a |
+% We can allow half-measure beams
+\set Timing.beamHalfMeasure = ##t
+r4. a8 a a |
@end lilypond
@i{@strong{How automatic beaming works}}
--- /dev/null
+\version "2.15.31"
+
+\header {
+
+ doctitle = "Special beaming rules for 3/4 time"
+
+ texinfo = "
+Whole-measure and half-measure beaming in 3/4 time can be controlled.
+The first measure should be beamed in one. The second measure should
+be beamed in three. The third and fourth measures should be beamed
+at 3/8.
+ "
+
+}
+
+\relative c' {
+ \time 3/4
+ c8^\markup "Beam in one" c c c c c
+ \set Timing.beamWholeMeasure = ##f
+ c8^\markup "Beam in three" c c c c c
+ \set Timing.beamHalfMeasure = ##t
+ r4.^\markup "Beam in Two" c8 c c
+ c8 c c r4.
+}
\new Staff{
\relative c' {
- \overrideTimeSignatureSettings
+ \overrideTimeSignatureSettings
#'(4 . 4) % time signature fraction
#'(1 . 4) % base moment fraction
#'(1 1 1 1) % beatStructure
#'(3 . 4) % time signature fraction
#'(1 . 4) % base moment fraction
#'(1 1 1) % beatStructure
- #'() % beamExceptions
+ #'((end . (((1 . 8) . (2 2 2))))) % set exceptions to beam by 1/4
\time 4/4
c8^\markup {"Beam by 1/4"} c c c c c c c |
\time 3/4
beatStructure = #'(1 1 1 1)
beamExceptions = #'((end . (((1 . 8) . (4 4))
((1 . 12) . (3 3 3 3)))))
+ beamWholeMeasure = ##t
+ beamHalfMeasure = ##f
+
autoBeaming = ##t
autoBeamCheck = #default-auto-beam-check
;;;; along with LilyPond. If not, see <http://www.gnu.org/licenses/>.
;; Determine whether an auto beam should be extended to the right
-;; of the current stem. We start anywhere except on the last note
-;; of a beat. We end according to the follwing rules, in order
-;; of decreasing priority:
+;; of the current stem. In general, we start anywhere except on
+;; the last note of a beat. We end according to the follwing rules,
+;; in order of decreasing priority:
;;
;; 1. end <type>
;; 2. end <greater type>
(define (beat-end? moment beat-structure)
(pair? (member moment beat-structure))) ;; member returns a list if found, not #t
+ (define (use-special-3-4-rules? fraction base-moment exceptions)
+ "Should we use special 3/4 time signature beaming rules?"
+ (and (equal? fraction '(3 . 4))
+ (equal? base-moment (ly:make-moment 1 4))
+ (null? (assoc-get '(1 . 8) exceptions '()))))
+
;; Start of actual auto-beam test routine
;;
;;
'())
beaming<?))
(function (if (= dir START) 'begin 'end))
+ (beam-whole-measure (get 'beamWholeMeasure #t))
+ (beam-half-measure (get 'beamHalfMeasure #f))
(type (moment->fraction test-beam))
(non-grace (ly:make-moment
(ly:moment-main-numerator measure-pos)
exception-grouping 0 grouping-moment)))
(if (= dir START)
- ;; Start rules
- (or (not (equal? time-signature-fraction '(3 . 4))) ;; start anywhere if not 3/4
+ ;; Start rules -- start anywhere unless 3/4 with default rules
+ ;; #t if beam is to start
+ (or (not (use-special-3-4-rules?
+ time-signature-fraction
+ base-moment
+ exceptions)) ;; start anywhere if not default 3/4
(= (ly:moment-main-numerator pos) 0) ;; start at beginning of measure
- (not (null? exception-grouping)) ;; don't use special rules if exception
- (beat-end? pos beat-endings) ;; are we at start of beat?
+ (and beam-half-measure
+ (equal? type '(1 . 8))
+ (equal? pos (ly:make-moment 3 8))) ;; start at mid-measure if 1/8 note beam
+ (beat-end? pos beat-endings) ;; start if at start of beat
(and (not (equal? test-beam base-moment)) ;; is beat split?
(not (beat-end? (ly:moment-add pos test-beam)
beat-endings)))) ;; will this note end the beat
- ;; End rules
+ ;; End rules -- #t if beam is to end
(or (= (ly:moment-main-numerator pos) 0) ;; end at measure beginning
- (if (null? exception-grouping)
- (beat-end? pos beat-endings) ;; no exception, so check beat ending
- (member pos exception-moments))))))) ;; check exception rule
+ (if (use-special-3-4-rules?
+ time-signature-fraction
+ base-moment
+ exceptions)
+ ;; special rule for default 3/4 beaming
+ (if (and (equal? type '(1 . 8))
+ (or beam-whole-measure
+ (and beam-half-measure
+ (not (equal? pos (ly:make-moment 3 8))))))
+ #f
+ (beat-end? pos beat-endings))
+ ;; rules for all other cases -- check for applicable exception
+ (if (null? exception-grouping)
+ (beat-end? pos beat-endings) ;; no exception, so check beat ending
+ (member pos exception-moments)))))))) ;; check exception rule
@code{\\autochange}.")
(beamExceptions ,list? "An alist of exceptions to autobeam rules
that normally end on beats.")
+ (beamHalfMeasure ,boolean? "Allow a half measure of eighth notes to
+be beamed together in 3/4 time?")
+ (beamWholeMeasure ,boolean? "Allow a whole measure of eighth notes
+to be beamed together in 3/4 time?")
(beatStructure ,list? "List of @code{baseMoment}s that are combined
to make beats.")
;;; NOTE: numerator is kept in beam-type because of
;;; tuplets, e.g. (2 . 24) = (2 . 3) * (1 . 8)
;;; for eighth-note triplets.
+;;;
(define-public default-time-signature-settings
'(
((beamExceptions . ((end . (((1 . 32) . (8 8 8 8 8 8))))))))
;; in 3 4 time:
- ;; use defaults, but combine all beats into a unit if possible
+ ;; use defaults -- no entries necessary
;;
- ;; set all beams to end on beats, but 1 8 to beam entire measure
- ;; in order to avoid beaming every beam type for the entire measure, we set
- ;; triplets back to every beat.
+ ;; Whole measure beaming is controlled by context property
+ ;; beamWholeMeasure
+ ;; Half measure beaming is controlled by context property
+ ;; beamHalfMeasure
+
((3 . 4) .
- ((beamExceptions . ((end . (((1 . 8) . (6)) ;1/8 note whole measure
- ((1 . 12) . (3 3 3)))))))) ;Anything shorter by beat
+ ((beamExceptions . ())))
;; in 3 8 time:
;; beam entire measure together
"Like the C++ code that executes \\override, but without type
checking."
(begin
- (revert-property-setting context property setting)
(ly:context-set-property!
context
property
;; body of revert-property-setting
(let ((current-value (ly:context-property context property)))
- (if (> (entry-count current-value setting) 1)
+ (if (> (entry-count current-value setting) 0)
(ly:context-set-property!
context
property
projects / lilypond.git / commitdiff