\version "2.18.2"


% What do you want to achieve with this function?

% return an object containing markup and score
exampleA =
#(define-scheme-function (parser location) ()
   ; create a
   (list
    (cons
     'mup
     #{
       \markup "Test"
     #})
    (cons
     'mus
     #{
       \score {
         c'4
       }
     #})
    ))

exA = \exampleA

% this is much nicer in 2.19.82 ...
$(ly:assoc-get 'mup exA)
$(ly:assoc-get 'mus exA)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% add the markup and the score immediatly
exampleB =
#(define-scheme-function (parser location) ()
   (add-score (ly:parser-clone parser)
     (list #{
       \markup "Test"
       #}))
   (add-score (ly:parser-clone parser)
     #{
       \score {
         c'4
       }
     #}
     ))

\exampleB


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% return a function that adds markup and score
exampleC =
#(define-scheme-function (parser location) ()
   (define-void-function (parser location)()
     (add-score (ly:parser-clone parser)
       (list #{
         \markup "Test"
         #}))
     (add-score (ly:parser-clone parser)
       #{
         \score {
           c'4
         }
       #}
       )))

exC = \exampleC

\exC