apply example

[Rune Zedeler]

Hi list!
Made an a bit more fancy example of how to hack "apply".
The transformer is to be used in music with the same rhythm used a lot
on different tones.
Store the "rhythm" in a variable using c' instead og the "first" note,
d' instead of the "second" note, etc...
Use as

\apply #transform { \rhythm {first second third etc...}
                    \rhythm {first second third etc...}
                    \rhythm {first second third etc...}
}

The #1 example of this is Bach Praeludium 1 in c-major.
After finishing the Praeludium I found out that it was already placed on
mutopia... Bad luck... But then, on the other hand, one can compare the
two and see how much typing you save by using the transformer.
Further more this also makes it easier to change something in the
rhythm.
For instance I found problems with dots dissappearing below the slurs.
Then I changed d8. to d16~d8 (not included here). It was soo easy. Just
one change, and the entire score changed.
In this example I have only one rhythm but one could easily define many
rhythms and switch between them during the score.

-Rune

\include "deutsch.ly"
\include "transform.ly"

\header{
  title =  "Preludium";
  opus =   "BWV 846";
  composer = "Johann Sebastian Bach (1685-1750)";
  enteredby = "Rune Zedeler";
  mutopiatitle = "Das Wohltemperierte Clavier I, Prelude 1 (c-major)";
  mutopiacomposer = "J.S.Bach";
  mutopiaopus = "BWV846";
  mutopiainstrument = "Piano";
  style = "baroque";
  copyright = "Public Domain";
  maintainer = "address@hidden";
  lastupdated = "2001/mar/30";
  tagline = "\\parbox{\hsize}{\\thefooter\\quad\\small \\\\This music is part 
of the Mutopia project, \\texttt{http://www.mutopiaproject.org/}\\\\It has been 
typeset and placed in the public domain by " + \maintainer + ".\\\\Unrestricted 
modification and redistribution is permitted and encouraged---copy this music 
and share it!}";
}

\version "1.3.142";

pat = \notes \transpose c'' \repeat unfold 2 {
  < { \context Staff=up {r8 e16 f g e f g } }
    { \context Staff=down <
      \context Voice=vup  { \stemUp \tieUp r16 d8.~d4 }
      \context Voice=vdwn { \stemDown  c2 }
    > }
  >
}

enda = \notes { r8 f,16 a, c f c a, \stemUp c \translator Staff = down
      a, f, a, f, d, f, d, \translator Staff = up \stemBoth
      r8 g16 h d' f' d' h d' h g h d f e-\prall d <e1 g c'^\fermata> \bar "|.";
}
endb = \notes {\stemUp \tieUp r16 c,8.~c,4~c,2 r16 h,,8.~h,,4~h,,2 c,1 \bar 
"|.";}
endc = \notes {\stemDown \tieDown c,,2~c,, c,,~c,, c,,1_\fermata }

\score {
  \notes \transpose c'' \context PianoStaff <
    \context Staff=up   { \clef "G"; s1*32 \enda }
    \context Staff=down { \clef "F"; s1*32 < \context Voice=vup \endb
                                             \context Voice=vdwn \endc
                        > }
    { \apply #transform {\pat {c e g c' e' }
                         \pat {c d a d' f' }
                         \pat {h, d g d' f' }
                         \pat {c e g c' e' }
                         \pat {c e a e' a' }
                         \pat {c d fis a d'  }
                         \pat {h, d g d' g' }
                         \pat {h, c e g c' }
                         \pat {a, c e g c'  }
                         \pat {d, a, d fis c' }
                         \pat {g, h, d g h }
                         \pat {g, b, e g cis'  }
                         \pat {f, a, d a d' }
                         \pat {f, as, d f h }
                         \pat {e, g, c g c' }
                         \pat {e, f, a, c f }
                         \pat {d, f, a, c f }

                         \pat {g,, d, g, h, f }
                         \pat {c, e, g, c e }
                         \pat {c, g, b, c e }
                         \pat {f,, f, a, c e  }
                         \pat {fis,, c, a, c es }
                         \pat {as,, f, h, c d }
                         \pat {g,, f, g, h, d }
                         \pat {g,, e, g, c e }
                         \pat {g,, d, g, c f }
                         \pat {g,, d, g, h, f }
                         \pat {g,, es, a, c fis }
                         \pat {g,, e, g, c g }
                         \pat {g,, d, g, c f }
                         \pat {g,, d, g, h, f }
                         \pat {c,, c, g, b, e }
                        }
    }
  >
  \paper {
    \translator {
      \PianoStaffContext
      VerticalAlignment \override #'forced-distance = #10
    }

    linewidth = 18.0 \cm;
  }
  \midi {
      \tempo 4 = 80;
  }
}

#(define (transform music)
  (let* ((es (ly-get-mus-property music 'elements))
         (n  (ly-music-name music))
        )
   (if (not (equal? n "Sequential_music"))
     (ly-warn "transform needs sequential music!")
     (begin
      (let recurse ((elts es))
       (if (not (equal? elts '()))
         (begin
           ((trans (ly-get-mus-property (cadr elts) 'elements)) (car elts))
           (set-cdr! elts (cddr elts))
           (recurse (cdr elts))
         )
       )
      )
     )
   )
   music
  )
 )

#(define ((trans pitches) music)
  (let* ((es (ly-get-mus-property music 'elements))
         (e (ly-get-mus-property music 'element))
         (p (ly-get-mus-property music 'pitch))
         (body (ly-get-mus-property music 'body))
         (alts (ly-get-mus-property music 'alternatives)))

    (if (pair? es)
        (ly-set-mus-property
         music 'elements
         (map (trans pitches) es)))

    (if (music? alts)
        (ly-set-mus-property
         music 'alternatives
         ((trans pitches) alts)))

    (if (music? body)
        (ly-set-mus-property
         music 'body
         ((trans pitches) body)))

    (if (music? e)
        (ly-set-mus-property
         music 'element
         ((trans pitches) e)))

    (if (pitch? p)
       (let* ((o (pitch-octave p))
              (n (pitch-notename p))
              (i (+ (* 7 o) n))
              (pes (ly-get-mus-property (list-ref pitches i) 'elements))
              (pnew (ly-get-mus-property (car pes) 'pitch))
             )
          (ly-set-mus-property music 'pitch pnew)
        )
    )
    music
  )
 )