dynamics and midi

[Grammostola Rosea]

Hi,

I made some score for my mama for practicing  vocals....  How do I get 
those  dynamics in  the midi  output?



staffSoprano = \new Staff  {
   \time 4/4
       \set Staff.instrumentName="Soprano"
   \set Staff.midiInstrument="choir aahs"
   \key d \major
   \clef treble
       \relative c' {     
       \context Voice = "melodySop" {
           \dynamicUp        
% Type notes here
\autoBeamOff
g''1 | fis2 r2 | g4.\ff g8 g4 g4 | g2. g4 | e4.\p e8 fis2 |
cis4. cis8 d4 fis | fis1 | e2 r4 a,4\f | fis'2. fis4 | e2. e8 e | g2 g4 
g | fis2. fis8 fis |
g2. g4 | fis8. a16 a8 a fis4 d | a2 r4 e'8\p e | e2. e4 |

       }

   \bar "|."
   }

}


\score {
   <<
       \staffSoprano
       
       
   >>
  
   \midi {
   }

   \layout  {
   }
}

\paper {
}