midi omits one instrument in full score

[Qian Li]

Hi, I've copied my complete code at the bottom, but the highlighted part is this. The midi plays the piano part only.

violasmiling  =                                                               
\relative c' {                                                                
    \set Staff.instrumentName = "Viola "                                      
        \clef alto                                                            
        \time 4/4                                                             
        \once \override TextScript #'padding = #2.2                           
        r8 [...]

        \score {
            <<
                %tag is viola
                \new StaffGroup
\keepWithTag #'score
\new Staff {\set Staff.midiInstrument = "viola" \violasmiling}
[...]

I've tried repositioning the \set Staff.midiInstrument everywhere but I never hear the part. 

Qian

*****************************
file: smiling.ly

\version "2.10.10"                                                            
\include "english.ly"
            
    
%identifiers                                                                  
Left = {\set stemLeftBeamCount = #1 }                                         
Right = {\set stemRightBeamCount = #1 }                                       
ssp = {\set stemLeftBeamCount = #1 \set stemRightBeamCount = #1 }             
ss = {\set stemLeftBeamCount = #1 \set stemRightBeamCount = #1 }              
Rests = {\override Rest #'transparent = ##t}                                  
global= { \time 4/4 }                                                         
OctBass = {#(set-octavation -1)}
EndOct = {#(set-octavation 0)}                                                
                
%music contents organized as identifiers
violasmiling  = 
\relative c' {                                                                
    \set Staff.instrumentName = "Viola "                                      
        \clef alto                                                            
        \time 4/4
        \once \override TextScript #'padding = #2.2                           
        r8^\markup
        {           
            \column{    
                \line{\bold "Boldly speeding " \tiny \note #"4" #0.7 "= 120"} 
                \line{\italic "n.v."}                                         
            }
        }   
    e\upbow \f d fs, fs'4 d|
        fs,8 e'( d g,) fs'( cs d4)|                                           
        r8 fs\downbow \mf cs d4. r8 e16(\downbow fs) |                        
        e8 d fs-> cs d4. e,16(\downbow fs)|                                   
        e8 d f-> cs d4 r|                                                     
        c?8\p a'4 g8~_\markup{\italic{vibrato}} g2~|                          
        g1 |
        g8 e'4 d8~^\markup{\italic{vibrato}} d2 |                             
        \bar "|." }
        %top piano staff
        uppersmiling = \relative c' {
            \clef treble
                \key c \major
                \time 4/4

                <bs c>16_\markup {\italic "Turbulent and percussive"} d r8 r8. e16 r8. e16 <e f> gf r8|
                r8. gf16( e gf e) r r4 r8. \clef bass <cs,-. d>16 |
                r8.  <cs-. d>16 r <bs cs>8 <cs-. d>16 <es fs> g <es fs> g cs d r8|
                r2 r8 d, e16 <fs g> r <e fs>|
                d8 e16 <fs g> r <e fs>[ \ssp r <e fs>] <e fs>16[ \ssp r <e fs> ] r r <e fs>[ \ssp r <e fs>] |
                \clef treble <f' g f' g>2 r4 r16
%phrasing slur tweak across staves
\once\override Slur  #'extra-offset = #'(0 . 6)
        \once\override Slur  #'control-points =
%( . openslur inversion) (openslur curve ) (curve body) (endpoint x . y)  
        #'((0 . -2) (0 . -1) (8 . 3) (15 . -13))
 <a b a' b>( <gs gs' a> <d' e d, e>_\markup {\italic "L.H."}|
                <a b a, b>4 r16)
\once\override Slur  #'extra-offset = #'(1 . 5)
        \once\override Slur  #'control-points =
        #'((-0.2 . -2) (0 . 0) (2 . 2) (6 . -13))

<a' b a, b>8( r16) r8. <a b a, b>16 r <gs, gs' a> r8|
                <f, g f' g>4 r16 <a' b> <gs a> <d e> <a b>8 r <a b> r|

        }

%bottom piano staff
lowersmiling = \relative c {
    \clef bass
        \key c \major
        \time 4/4

        r8. <bs cs>16 <bs cs> d r8 r4 r8  <cs d>8 |
        fs,16 <bs, cs> d8 r8. <bs cs>16 d( <es fs> g?8~) g4|
        \OctBass <cs, cs,>8 <d d,> <cs cs,>  <d d,> \EndOct r4 <fs' fs,>8 <cs cs,>16 <d d,>~ |
        <d d,>8. d,16 e <fs g> r8 r2|
        r4 <d d'>16 r8. <d d'>16 r8. d16[ \ssp r d] r|
        r <cs cs'> <d d'>8~ <d d'>4 r16 <cs cs'><d d'> <cs cs'> r4|
        r16 <cs' b cs'>16 <d d'>8 r <cs b cs'>16 <d d'> r8 <cs b cs'>16 r <d d'> r8.|
        r16 cs, d cs d4 r8 <cs' b>16 d r8 <cs b>16 d


}

%tagging separates the 2 parts in violapart and pianopart.ly

music = {
    <<

        \tag #'score \tag #'vla \new Staff { << \global \set Staff.midiInstrument = "viola" \violasmiling>> }
    %obligatory tag for piano staves not to be printed anyway
        \tag #'score \tag #'topp \new PianoStaff { << \global \uppersmiling >> }
    \tag #'score \tag #'botp \new PianoStaff { << \global \lowersmiling>> }
    >>
}

******************end smiling.ly

file: document.ly *this is the file I compile

\version "2.10.10"

\include "english.ly"

%including the music content
\include "smiling.ly"
\include "scordatura.ly"
\include "144.ly"
\include "energy.ly"
\include "chords.ly"

%for scordatura mvt 2
tuning = \markup {
    \score {
        \new Staff \with {
            \remove Time_signature_engraver
        } {
            \clef alto  <d g d' a'>1
        }
        \layout { ragged-right = ##t }
    }
}

%%  makes sure text scripts and lyrics are within the paper margins
%\override Score.PaperColumn #'keep-inside-line = ##t

#(set-global-staff-size 14)
\book{
    \header
    {
        title = "Microtures for viola and piano"
            composer = "Qian Li"
    }

    %smiling movement
        \score {
            <<
                %tag is viola
                \new StaffGroup
\keepWithTag #'score
\new Staff {\set Staff.midiInstrument = "viola" \violasmiling}
                %this is piano
                \new PianoStaff <<
                \new Staff = "upper" \uppersmiling
                \new Staff = "lower" \lowersmiling

                >>
                >>
                \layout { }
            \midi {
                \context {
                    \Score
                        tempoWholesPerMinute = #(ly:make-moment 120 4)
                }
            }
            \header
            {
                piece = "mvt. 1"
            }

        }

    %2nd movement
[etc. from other files]

%end book
}