Articulate.ly - Fix Mordents and Pralltriller

Mordents should be on-beat, not grace notes.  And pralltrillers
(half-shakes) are always either 4 alternating notes, or an inverted
mordent.

There is of course a general problem here in that the way ornaments
are realised has changed through the centruries.  Even Bach and Clementi
disagree! I'm following CPE Bach's 'True art of the Keyboard Playing'
in the interpretation here.  To do the job properly we'd have two
articulations: \prall and \inverted_mordent and treat them
separately for MIDI, but typeset the same glyph.

diff --git a/ly/articulate.ly b/ly/articulate.ly
index 3cd98f4436da19cf8d096a8fb9dfc30e7318770c..59424e515216b95776e038dadf653566ab25b3cb 100644 (file)
--- a/ly/articulate.ly
+++ b/ly/articulate.ly
@@ -394,7 +394,7 @@
         ((string= articname "mordent")
          (loop (cons 1 1) newelements tail (cons 'mordent actions)))
         ((string= articname "prall")
-         (loop (cons 1 1) newelements tail (cons 'trill actions)))
+         (loop (cons 1 1) newelements tail (cons 'prall actions)))
         ((string= articname "trill")
          (loop (cons 1 1) newelements tail (cons 'trill actions)))
         ((string= articname "turn")
@@ -516,27 +516,77 @@
        ((trill)
         (ac:trill music))
 
+       ((prall)
+       ; A pralltriller symbol can either mean an inverted mordent
+       ; or a half-shake -- a short, two twiddle trill.
+       ; We implement as a half-shake.
+       (let*
+        ((totallength (ly:music-length music))
+         (newlen (ly:moment-sub totallength (ly:make-moment 3 32)))
+         (newdur (ly:make-duration
+                  0 0
+                  (ly:moment-main-numerator newlen)
+                  (ly:moment-main-denominator newlen)))
+         (gracedur (ly:make-duration 5 0 1 1))
+         (gracenote (ly:music-deep-copy music))
+         (abovenote (ly:music-deep-copy music))
+         (mainnote (ly:music-deep-copy music))
+         (prall (make-sequential-music (list gracenote abovenote)))
+       )
+         (music-map (lambda (n)
+          (if (eq? 'NoteEvent (ly:music-property n 'name))
+            (set! (ly:music-property n 'duration) gracedur))
+                     n)
+          abovenote)
+         (music-map (lambda (n)
+          (if (eq? 'NoteEvent (ly:music-property n 'name))
+            (set! (ly:music-property n 'duration) gracedur))
+                     n)
+          gracenote)
+         (music-map (lambda (n)
+          (if (eq? 'NoteEvent (ly:music-property n 'name))
+            (set! (ly:music-property n 'duration) newdur))
+                     n)
+          mainnote)
+
+         (map (lambda (y) (ac:up y))
+          (filter
+           (lambda (z) (eq? 'NoteEvent (ly:music-property z 'name)))
+           (ly:music-property abovenote 'elements)))
+         (make-sequential-music (list abovenote gracenote abovenote mainnote))))
+
        ((mordent)
        (let*
-        ((dur (ly:music-property
+        ((totaldur (ly:music-property
                (car (ly:music-property music 'elements)) 'duration))
-         (factor (ly:duration-factor dur))
+         (dur (ly:duration-length totaldur))
+         (newlen (ly:moment-sub dur (ly:make-moment 2 32)))
+         (newdur (ly:make-duration
+               0 0
+                  (ly:moment-main-numerator newlen)
+                  (ly:moment-main-denominator newlen)))
          (gracenote (ly:music-deep-copy music))
-         (mainnote (ly:music-deep-copy music))
          (belownote (ly:music-deep-copy music))
+         (mainnote (ly:music-deep-copy music))
          (mordent (make-sequential-music (list gracenote belownote)))
-)
+       )
         (begin
          (music-map (lambda (n)
           (if (eq? 'NoteEvent (ly:music-property n 'name))
-           (set! (ly:music-property n 'duration)(ly:make-duration 3 0 1 1)))
+           (set! (ly:music-property n 'duration)
+            (ly:make-duration 5 0 1 1)))
                      n)
           mordent)
+         (music-map (lambda (n)
+          (if (eq? 'NoteEvent (ly:music-property n 'name))
+            (set! (ly:music-property n 'duration) newdur))
+                     n)
+          mainnote)
          (map (lambda (y) (ac:down y))
           (filter
            (lambda (z) (eq? 'NoteEvent (ly:music-property z 'name)))
            (ly:music-property belownote 'elements)))
-         (make-sequential-music (list (make-grace-music mordent) mainnote)))))
+         (make-sequential-music (list mordent mainnote)))))
        ((turn)
        (let*
         ((dur (ly:music-property