Call a score variable by a scheme expression

[Marc Hohl]

Hello list,

I think this has been answered before, but I don't find it in the 
archives...

Assume I have the following file scoretest.ly:

\version "2.17.10"

#(define opt-score (or (ly:get-option 'score) "Full"))

musicA = \relative f {
  c''4 d e f | g1
}

musicB = \relative f {
  c'4 b a f | g 2 g
}

testScoreA = \score {
  \new Staff { \musicA }
}

testScoreB = \score {
  \new Staff { \musicB }
}

testScoreFull = \score {
  <<
    \new Staff { \musicA }
    \new Staff { \musicB }
  >>
}

\score {
  #(string-append "testScore" opt-score)
}

I want to call this file either by lilypond without options,
which should yield in calling \testScoreFull in the \score { ... },
or by 'lilypond -dscore="A" testscore.ly' to obtain \score { \testScoreA },
'lilypond -dscore="B" testscore.ly' should produce \score { \testScoreB }.

The test file does not work, and I am sure that I have seen
something very similar somemonths ago, but I don't find it right now.

Any hints are highly welcome!

Thanks in advance,

Marc