score in a music function?

[Stefan Thomas]

Dear community,
is it possible to have the score command in a music function?
I need it for a piece with different movements.
I've tried it with the following code which doesn't work:

\version "2.16.2"
TheScore = #(define-music-function (parser location x y) (ly:music? ly:music?)
  #{ 
   \score {
      \new StaffGroup
      <<
    \new Staff \with { instrumentName = "first" } $x
    \new Staff \with { instrumentName = "second" } $y
      >>
    }
#})

first = \relative c' { c4 d e f g1 }
second = \relative c'' { g4 f e d c1 }

  \TheScore \first \second