Re: Selected pieces in a book

[Simon Albrecht]

Hello Pierre,

On 10.10.2015 19:41, Pierre Perol-Schneider wrote:
> Hi LilyPonders,
>
> I'm trying to automagically select pieces within a library.
> My first intention was to use 'tags' but it does not seem to work a 
> that level.

\tag is a music function, so it can’t output scores.

> Any idea how to achieve that ?

I’d use some Scheme code:

%%%%%%%%%%%%%%%%%%%%%%
\version "2.19.28"

my-first-piece = \relative c' {
  \mark "Level 1"
  c1 d e f g a b c
}

my-second-piece = \relative c' {
  \mark "Level 1"
  c2 d e f g a b c
}

my-third-piece = \relative c' {
  \mark "Level 2"
  c4 d e f g a b c
}

my-fourth-piece = \relative c' {
  \mark "Level 2"
  c8 d e f g a b c
}

%% define scheme lists of music expressions for each level
#(define level-one (list my-first-piece my-second-piece))
#(define level-two (list my-third-piece my-fourth-piece))

#(define (print-by-level lst)
   ;; wrap each music expression into \score {}
   ;; and add each of the scores to the bookpart
   (let ((print-piece (lambda (mus)
                        #{ \score { $mus } #})))
     ;; see ‘scm/lily-library.scm’ for add-score
     ;; (and many other useful procedures)
     (map add-score (map print-piece lst))))

%% Select pieces by level:
\book {
  \bookpart {
    %% Select only 'level 1 pieces':
    #(print-by-level level-one)
    %}
    \header {
      title = "Level I"
    }
  }
  \bookpart {
    %% Select only 'level 2 pieces':
    #(print-by-level level-two)
    %}
    \header {
      title = "Level II"
    }
  }
}
%%%%%%%%%%%%%%%%%%%

It has been a personal breakthrough to discover the use of these 
functions from lily-library.scm…
I hope you can make sense and use of that :-)

Yours, Simon