Re: make-span-event

[Nicolas Sceaux]

Juergen Reuter <address@hidden> writes:

> Hi!
>
> Maybe this is a silly question, but there is something that I do not quite 
> understand.  I am trying to create span events in a music function:
>
> \version "2.4.0"
> crescendo = #(def-music-function
>              (location music) (ly:music?)
>              (make-music 'SequentialMusic
>                          'elements (list
>                                     (make-span-event 'CrescendoEvent START)
>                                     music
>                                     (make-span-event 'CrescendoEvent STOP))))
>
> crescendoStart = #(make-span-event 'CrescendoEvent START)
> crescendoStop = #(make-span-event 'CrescendoEvent STOP)
>
> \score {
>   <<
>     { c d\crescendoStart e\crescendoStop f }
>     { c \crescendo { d e } f }
>     { c d\cr e\endcr f }
>   >>
> }
>
> In this example, the predefined \cr and \endcr work well; also do the 
> locally defined \crescendoStart and \crescendoStop.  However, although the 
> \crescendo music function uses exactly the same scheme expressions for 
> creating span events, applying the \crescendo function does not show any 
> effect.  What I am doing wrong?

You can find out by comparing the two music expressions:

guile> (mus:display #{ \notemode { d\cr e\endcr } #})
(make-music 'SequentialMusic
  'elements (list
             (make-music 'SequentialMusic
               'elements (list
                          (make-music 'EventChord
                            'elements (list
                                       (make-music 'NoteEvent
                                         'duration (ly:make-duration 2 0 1 1)
                                         'pitch (ly:make-pitch -1 1 0))
                                       (make-music 'CrescendoEvent
                                         'span-direction -1)))
                          (make-music 'EventChord
                            'elements (list
                                       (make-music 'NoteEvent
                                         'duration (ly:make-duration 2 0 1 1)
                                         'pitch (ly:make-pitch -1 2 0))
                                       (make-music 'CrescendoEvent
                                         'span-direction 1)))))))

guile> (mus:display #{ \crescendo \notemode { d e } #})
(make-music 'SequentialMusic
  'elements (list
             (make-music 'SequentialMusic
               'elements (list
                          (make-music 'CrescendoEvent
                            'span-direction -1)
                          (make-music 'SequentialMusic
                            'elements (list
                                       (make-music 'EventChord
                                         'elements (list
                                                    (make-music 'NoteEvent
                                                      'duration 
(ly:make-duration 2 0 1 1)
                                                      'pitch (ly:make-pitch -1 
1 0))))
                                       (make-music 'EventChord
                                         'elements (list
                                                    (make-music 'NoteEvent
                                                      'duration 
(ly:make-duration 2 0 1 1)
                                                      'pitch (ly:make-pitch -1 
2 0))))))
                          (make-music 'CrescendoEvent
                            'span-direction 1)))))


Note where the CrescendoEvents are placed in both cases.

nicolas