Can't get the voices right with \stemUp and \stemDown

[ario]

Hello all,
Trying to write a piece for 4 voices choir, I'm stuck with
the problem that the stems won't stand in the right direction.
Wherever I put those \stemUp en \stemDown commands, they just 
don't seem to have the desired effect.
I want the sopranos and the tenors have their stem up, and the 
altos and basses stem down. Hoping that then the slurs will
come out fine too (finally).

The music consists of 4 files:
main file,
header file,
melodies file,
texts file
as copy/pasted below.

Would somebody be able to give me the solution?
Thanks a lot.
arie


Main file 'wa_loezjag_4.1.ly':
================================================
% wa_loezjag_4.1.ly

\include "nederlands.ly"
\include "wl_h_4.1.ly"
\include "wl_m_4.1.ly"
\include "wl_t_4.1.ly"


sopAltTotal = \simultaneous
{
   \addlyrics
   \context Staff = SopAlt
   { 
      \property Staff.instrument = "sop-alt"
      \property Staff.midiInstrument = "voice oohs"
      \clef "treble"
      \property Staff.automaticMelismata = ##t
      \notes
         \context Voice = soprano
         < 
            \global
            \stemUp
            \sopranoMelody  % see file wl_m_x.x.ly 
            \stemDown
            \altoMelody     % see file wl_m_x.x.ly
         >
   }

   \context Lyrics = one
   < 
       \context LyricsVoice = "soprano-one-FO"
       {   \property  LyricsVoice.stanza = "1 fo"   
           \property LyricsVoice . LyricText \override #'font-name = #"cmr9"
           \textOneFO
       }

       \context LyricsVoice = "soprano-one-RU"
       {   \property  LyricsVoice.stanza = "1 ru"
           \property LyricsVoice . LyricText \override #'font-name = #"wncyr10"
           \textOneRU
       }

       \context LyricsVoice = "soprano-two-FO"
       {   \property  LyricsVoice . stanza = "2 fo"   
           \property LyricsVoice . LyricText \override #'font-name = #"cmr9"
           \textTwoFO
       }

       \context LyricsVoice = "soprano-two-RU"
       {   \property  LyricsVoice . stanza = "2 ru"
           \property LyricsVoice . LyricText \override #'font-name = #"wncyr10"
           \textTwoRU
       }

       \context LyricsVoice = "soprano-three-FO"
       {   \property  LyricsVoice . stanza = "3 fo"   
           \property LyricsVoice . LyricText \override #'font-name = #"cmr9"
           \textThreeFO
       }

       \context LyricsVoice = "soprano-three-RU"
       {   \property  LyricsVoice . stanza = "3 ru"   
           \property LyricsVoice . LyricText \override #'font-name = #"wncyr10"
           \textThreeRU
       }

       \context LyricsVoice = "soprano-four-FO"
       {   \property  LyricsVoice . stanza = "4 fo"
           \property LyricsVoice . LyricText \override #'font-name = #"cmr9"
           \textFourFO
       }

       \context LyricsVoice = "soprano-four-RU"
       {   \property  LyricsVoice . stanza = "4 ru"
           \property LyricsVoice . LyricText \override #'font-name = #"wncyr10"
           \textFourRU
       }
   >
}

tenBasTotal = 
    \context Staff = bass
    {
        \property Staff.instrument = "ten-bas"
        \property Staff.midiInstrument = "voice oohs"
        \clef "bass"
        \notes \context Voice=bass
        <
            \global
            \stemUp
            \tenorMelody    % see file wl_m_x.x.ly
            \stemDown
            \bassMelody     % see file wl_m_x.x.ly
        >
    }

\score
{
    \context ChoirStaff = choir
    <
        \sopAltTotal
        \tenBasTotal
    >

    \paper { % linewidth = 19.0 \cm 
           }
    \midi  { \tempo 4=120 }
}

% EOF
================================================

Header file 'wl_h_4.1.ly':
================================================
% wl_h_4.1.ly
% headers

\header {
 mutopiatitle = "Wo Loezjag"
 mutopiacomposer = "Russisch Volkslied"
 mutopiaarranger = "S. Tsariova"
 mutopiapoet = ""
 mutopiainstrument = "Choir SATB"
 date = ""
 source = "S.T. (ed.) typed"
 style = ""
 copyright = "Public Domain"
 maintainer = ""
 maintainerEmail = ""
 lastupdated = "2003-06-12"
  title="Wo Loezjag"
  composer="Russisch Volkslied"
  poet=""
  arranger = "Arr. S. Tsariova"

  footer = "A.V. 2003-06-13"
}

\version "1.6.2"

global = \notes {
   \time 2/4
   \key g \major
  % \skip 1*18 \bar "|."
}
==============================

Melodies file 'wl_m_4.1.ly':
==============================
% wl_m_4.1.ly
% melodies

sopranoMelody = \notes \relative c'' { \stemUp 
   d4.( e8   | [d8 e8 )d8 e8] | d4.( c8   | )b4 g4 | r4 d'4( | )e4 e4 | d4 b8 
d8 |
   c8( d16 )c16 b8 d8 | [a8 d8   d8 d8]   | 
   b4 b8 d8  | c8( d16 )c16 b8 d8 | [a8 d8   d8 d8]   | g,2  |  \bar ":|"  g'2  
\bar "|."
}

altoMelody = \notes \relative c'' { \stemDown
   b4.( c8   | [b8 c8 )b8 c8] | b4.( a8   | )g4 d4 | r4 g4(  | )g4 g4 | g4 g8 
g8 |
   g8( )a8      g8 b8 | [a8 fis8 g8 a8]   |
   g4 g8 g8  | g8( )a8      g8 b8 | [a8 fis8 g8 a8]   | d,2  |  b2
}

tenorMelody = \notes \relative c' { \stemUp
   d4.( fis8 | [d8 e8 )d8 e8] | d4.( e8   | )d4 b4 | r4 b4(  | )c4 c4 | b4 d8 
d8 |
   e8( )fis8    d8 d8 | [d8 d8   e8 d8]   |
   b4 d8 d8  | e8( )fis8    d8 d8 | [d8 d8   e8 d8]   | b2   |  d2
}

bassMelody = \notes \relative c' { \stemDown
   g2(       | )g4.      g8 | g2(         | )g4 g4 | r4 g4(  | )c4 c4 | g4 g8 
b8 |
   a8( )d,8     g8 g8 | [fis8 d8 e8 fis8] |
   g4 g8 b8  | a8( )d,8     g8 g8 | [fis8 d8 e8 fis8] | g2   |  g2
}
==============================

Texts file 'wl_t_4.1.ly':
==============================
% wl_t_4.1.ly
% texts

textOneFO = \lyrics {
   WA LOE -- ZJA--G, DA WA LOE -- ZJAG, 
   WA LOE-   ZJA-G, WA ZE-   LJO -- NYG WA LOE -- ZJAG.
   WA LOE -- ZJA-G, WA ZE -- LJO -- NYG WA LOE -- ZJAG.
}

textOneRU = \lyrics {
   Vo lu -- za--h, da vo lu -- zah, 
   vo lu-   za-h, vo ze-   le -- nyh vo lu -- zah.
   Vo lu -- za-h, vo ze -- le -- nyh vo lu -- zah.
}

textTwoFO = \lyrics {
   WY -- RA -- SLA, DA WY RA -- SLA, 
   WY -- RA-   STA-LA TRA -- WA SHO - LKA -- WA -- JA.
   WY -- RA -- STA-LA TRA -- WA SHO - LKA -- WA -- JA.
}

textTwoRU = \lyrics {
   Vy -- ro -- sla, da Vy ro -- sla,
   Vy -- ra-   sta-la tra -- ba xe - lko -- va -- ja.
   Vy -- ra -- sta-la tra -- ba xe - lko -- va -- ja.
}

textThreeFO = \lyrics {
   RA -- STSWE -- LIE, DA RA -- STSWE -- LIE,
   RA -- STSWE-   LIE TSWE -- TY LA -- ZO -- RJE -- WY -- JE.
   RA -- STSWE -- LIE TSWE -- TY LA -- ZO -- RJE -- WY -- JE.
}

textThreeRU = \lyrics {
   Ra -- scve -- li, da ra -- scve -- li,
   ra -- scve-   li cve -- ty la -- zo -- re -- vye.
   ra -- scve -- li cve -- ty la -- zo -- re -- vye.
}

textFourFO = \lyrics {
   TOE -- TRA -- WOE, DA TOE -- TRA -- WOE,
   OEZJ JA-   TOE -- TRA -- WOE WY -- KA -- SHOE KA -- SOJ.
   OEZJ JA -- TOE -- TRA -- WOE WY -- KA -- SHOE KA -  SOJ.
}

textFourRU = \lyrics {
   Tu -- tra -- vu, da tu -- tra -- vu,
   Uh a-   tu -- tra -- vu by -- ko -- xu ko -- soi.
   Uh a -- tu -- tra -- vu by -- ko -- xu ko -  soi.
}
==============================