\version "2.19.16"

%% Please note, \language has to be declared before 'used-language'
%% is done or included, (if stored elsewhere)
\language "deutsch"
%\language "english"
%% if no tagline for a language is defined, default-english will be printed
%\language "catalan"

%% TODO: find better method to detect which language is actually used
#(define used-language
   (car
    (find
     (lambda (e) (eq? (cdr e) (ly:parser-lookup parser 'pitchnames)))
     language-pitch-names)))

englishTaglineText = #(format #f
                        "Music typeset using LilyPond ~a~awww.lilypond.org"
                        (lilypond-version)
                        (ly:wide-char->utf-8 #x2014) ;; 2014 = em dash.
                        )
germanTaglineText = #(format #f
                       "Noten gesetzt mit LilyPond ~a ~a www.lilypond.org"
                       (lilypond-version)
                       (ly:wide-char->utf-8 #x2013) ;;2013 = en dash.
                       )

#(define taglines
   `(
      (deutsch . ,germanTaglineText)
      (english . ,englishTaglineText)
      ))

#(define-markup-command (format-tagline layout props text) (markup?)
   (interpret-markup layout props
     #{
       \markup {
         \italic
         \pad-to-box #'(0 . 0) #'(0 . 3)
         {
           \with-url #"http://lilypond.org/"
           $text
         }
       }
     #}))

#(define used-tagline
   (markup #:format-tagline
     (let ((tagl (assoc-get used-language taglines)))
       (if tagl
           tagl
           (assoc-get 'english taglines)))))

tagline = #used-tagline
getTagline = #(define-void-function
               (parser location lang) (string?)
               (set! tagline
                     (markup #:format-tagline
                       (let ((tagl (assoc-get (string->symbol lang) taglines)))
                         (if tagl
                             tagl
                             (begin
                              (ly:warning (format #f "Tagline for ~a not supported, using English." lang))
                              (assoc-get 'english taglines))))))
               ;(display tagline)
               )

\header {
  \getTagline "deutsch"

}

{ c''1 }