Re: Composing music functions

[Thomas Morley]

2017-03-12 22:46 GMT+01:00 Morten Lemvigh <address@hidden>:
> Hi,
>
> I'm trying to create some tools for setting choir pieces. I have run against
> a problem where I have a music function that needs the result of another
> music function. That other function uses a Lilypond code block, so it takes
> both parser and location. For reasons I don't understand, I cannot get this
> to work. Lilypond gives me a:
>
>   Wrong type to apply: #<Music function #<procedure #f (music)>>
>
>
> I have tried to create a small toy example to show what I want to achieve:
>
> rest-around = #(define-music-function (parser location music ) (ly:music?)
>   #{ r4 $music r4 #})
>
> restful-choir = #(define-music-function (parser location music) (ly:music?)
>   (let ((rest-around (rest-around parser location music)))
>    #{
>      <<
>        \new Voice { \voiceOne \transpose c g $rest-framed }

rest-framed is not defined see terminal-output:

error: GUILE signaled an error for the expression beginning here
       \new Voice { \voiceOne \transpose c g $
                                              rest-framed }
Unbound variable: rest-framed


>        \new Voice { \voiceTwo $rest-framed }
>      >>
>    #}))
>
>
> music =  { c' d' e' }
>
> \score {
>   \new Staff { \restful-choir \music }
> }
>
> I have run into this problem a couple of times, the current problem I'm
> trying to solve is: I have a list of music an I am trying to map each item
> of the list with a function that creates a staff with the music. Afterwards
> they should be combined as 'SimultaneousMusic. I would like to use Lilypond
> code blocks where I think it is clearer than the Scheme counterpart.
>
> Is there something obvious I am doing wrong,

You did not post your lily-version ;)

> or am I perhaps completely off
> on this approach...?
>
> Best regards,
> Morten

This works for newer devel-versions:

\version "2.19.56"

rest-around = #(define-music-function (music ) (ly:music?)
  #{ r4 $music r4 #})

restful-choir = #(define-music-function (music) (ly:music?)
  (let ((rest-framed (rest-around music)))
   #{
     <<
       \new Voice { \voiceOne \transpose c g $rest-framed }
       \new Voice { \voiceTwo $rest-framed }
     >>
   #}))


music =  { c' d' e' }

\score {
  \new Staff { \restful-choir \music }
}


Cheers,
  Harm