transposition and midi

[D Josiah Boothby]

Using 2.4.2, I'd like to be able to transpose a part, create a midi 
file, and create the graphical output. The midi output is transposed 
right along with the score if everything is in the same score block. Is 
it possible to have an untransposed midi with transposed parts without 
having to play games with comments or writing out more than one score 
block every time (as in the below example)?

firstNotes = \relative c'' { \key c \minor c4 b c2 }

secondNotes = \relative c'' { \key c \minor a4 gis a2 }

\score {
 \context StaffGroup <<
   \context Staff = "first" <<
     \transpose bes c'
     \firstNotes
   >>
   \context Staff = "second" <<
     \transpose f c'
     \secondNotes
   >>
 >>

 \layout { }
}

\score {
 \context StaffGroup <<
   \context Staff = "first" <<
     \firstNotes
   >>
   \context Staff = "second" <<
     \secondNotes
   >>
 >>
 \midi { \tempo 4 = 60 }
}