Re: rhythm template function

[Alard de Boer]

On Thu, May 22, 2008 at 5:09 AM, Jay Anderson <address@hidden> wrote:
> "Easy Rhythm Template Creation" added to the lsr. Thanks.
>
> -----Jay

Hi Jay,

I had some trouble getting tuplets to work with your snippet. Here's a modified
version that checks whether a tuplet (TimeScaledMusic) is used in the template,
and handles that case separately; see function make-chord-or-tuplet. I'm not
very good with Scheme, perhaps there is an easier way to do this?

Thanks again,
Alard.

---
\version "2.11.46"

%Rhythm template stuff
#(define (create-note pitch duration)
 (make-music 'NoteEvent
    'duration duration
    'pitch pitch))

#(define (make-chord chord-pitches chordevent)
 (let* ((skip (car (ly:music-property chordevent 'elements)))
        (rest (cdr (ly:music-property chordevent 'elements)))
        (duration (ly:music-property skip 'duration)))
   (if (eq? (ly:music-property skip 'name) 'SkipEvent)
     (make-music 'EventChord
       'elements (append
                   (map (lambda (x) (create-note x duration)) chord-pitches)
                   rest))
     chordevent)))

#(define (make-chord-or-tuplet pitches event)
 (if (eq? (ly:music-property event 'name) 'TimeScaledMusic)
   (make-music
    'TimeScaledMusic
    'denominator (ly:music-property event 'denominator)
    'numerator (ly:music-property event 'numerator)
    'element (make-music
              'SequentialMusic
              'elements (make-rhythm
                         pitches
                         (ly:music-property
                          (ly:music-property event 'element) 'elements))))
   (make-chord pitches event)))

#(define (make-rhythm pitches template)
 (cond ((null? template) '())
       ((ly:pitch? (car pitches))
         (cons
           (make-chord-or-tuplet pitches (car template))
           (make-rhythm pitches (cdr template))))
       (else
         (cons
           (make-chord-or-tuplet (car pitches) (car template))
           (make-rhythm (cadr pitches) (cdr template))))))

% Returns two pitches from the input:
%  ( <The original pitch(es)>
%    <The pitch(es) in octave '-1'> )
% This makes the function work in \relative sections
% To make it work outside of \relative only return p.
#(define (get-pitches mus)
 (let* ((p (map
             (lambda (x) (ly:music-property x 'pitch))
             (ly:music-property mus 'elements)))
        (first-p (car p))
        (pitch (ly:pitch-notename first-p))
        (alteration (ly:pitch-alteration first-p))
        (octave -1)
        (px (ly:make-pitch octave pitch alteration)))
   (list p (cons px (cdr p)))))

#(define (rhythm-template template)
 (define-music-function (parser location mus) (ly:music?)
   (make-music
     'SequentialMusic
     'elements (make-rhythm
                 (get-pitches mus)
                 (ly:music-property template 'elements)))))

%Example usage:
%These methods should only be used within a \relative section.
rhya = #(rhythm-template #{s8.-> s16 s8#} )
rhyb = #(rhythm-template #{s8[ r16 s16 s8]#} )
rhyc = #(rhythm-template #{s16 s~ s4#} )

rhyd = #(rhythm-template #{ \times 2/3 { s8 s8 s8 } s4 s4 s8 s8 s4 #} )
rhye = #(rhythm-template #{
    \times 2/3 { s8---\pp s8-- s8-- } s4-- s4-- s8-- s8-- s4-- #} )

\score
{
 \new Staff \relative c'
 {
   \time 6/8
   \rhya c \rhyb c |
   \rhya <c e> \rhyb <c f> |
   \rhyc <c e> \rhyc <c d> |
   \time 5/4
   \rhyd c
   \rhyd e
   \rhye <c e g>
 }
}


-- 
Groeten,
Alard.

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