\version "2.11.39"

IChorSettings = \notemode { \time 3/4 }
IChorPieceName = "Nr. 1 TEST"
IChorPieceNameTacet = "Nr. 1 tacet"

IChorFlI = \relative c' { <c e g>4 r2 g' a8 r8 r4\bar"|." }

clefFl = \clef "tenor"
IChorKey = \notemode { \key g \major }

IChorFlIStaff = \context Staff = IChorFlISt <<
    \clefFl
    \context Voice = IChorFlIVoice { \IChorSettings\IChorKey\IChorFlI }
    \set Staff.instrumentName = "Flauto I"
    \set Staff.shortInstrumentName = "Fl. I"
>>

IChorFlIScore = \score {
  << \IChorFlIStaff >>
  \header { piece = \IChorPieceName }
}

% This is the lilypond code, which I want to generate in scheme:
\score {
      << \IChorFlIStaff >>
      \header { piece = \IChorPieceName }
}

% My attempts of a scheme function to generate the score:
scr = #(define-music-function (parser location piece instr) (string string)
  #{ 
    \score {
      << #(eval (string->symbol (string-append piece instr #"Staff"))) >>
      \header { piece = #(eval (string->symbol (string-append piece #"PieceName"))) }
    }
  #}
)
% Call to that function:
\scr #"IChor" #"FlI"