Re: Apply event function *within* music-function

[Jan-Peter Voigt]

Hi Urs,

Am 02.05.2017 um 10:53 schrieb Urs Liska:
> ...
> What I did *not* manage yet is at the end of the thing.
> When I use
>
> test =
> #(define-music-function (mus)(ly:music?)
>    #{
>      <>\startGroup
>      #mus
>      <>\stopGroup
>    #})
>
> {
>   \test { c' d' e' f' } g' a' b' c'
> }
>
> the bracket includes the g' - or rather the zero-length chord
> immediately before it.
>
> Do you have any suggestion how to do *this* in a convenient manner, i.e.
> without splitting #mus into pieces and insert the \stopGroup before the
> last element?

this *is* kind of splitting the music, but just to show, where the 
closing articulation "NoteGroupingEvent" should be placed:

\version "2.19.57"

test =
#(define-music-function (mus)(ly:music?)
   (let* ((elms (ly:music-property mus 'elements))
          ; first and last music-element ...
          (frst (first elms)) ; TODO test for list? and ly:music?
          (lst (last elms)) ; TODO test for list? and ly:music?
          (fartic (ly:music-property frst 'articulations '())) ; look 
for eventchords ...
          (lartic (ly:music-property lst 'articulations '()))
          )
     (ly:music-set-property! frst 'articulations `(,@fartic 
,(make-music 'NoteGroupingEvent 'span-direction -1)))
     (ly:music-set-property! lst 'articulations `(,@lartic ,(make-music 
'NoteGroupingEvent 'span-direction 1)))
   #{
     #mus
   #}))

\new Staff \with {
  \consists "Horizontal_bracket_engraver"
} {
  \test { c' d' e' f' } g' a' b' c''
}


HTH
Jan-Peter