\version "2.17.17"

musicone = \relative c' { c'8( f d4) bes c g f | }
musictwo = \relative c' { a'4 bes g g c, c }
musicthree = \relative c' { c4 f d e g, a }

firstvoice =  {
  \key bes \major
  \time 6/4
  <>^"default"
  \musicone
  <>^"voices 1 3 2"
  \voiceOne
  \musicone
  <>^"voices 1 4 2"
  \musicone
  <>^"manual up/down"
  \stemUp
  \slurUp
  \musicone
}

secondvoice = \relative c' {
  \key bes \major
  % default
  \musictwo
  % voices 1 3 2
  \voiceThree
  \musictwo
  % voices 1 4 2
  \voiceFour
  \musictwo
  % manual up/down
  \oneVoice
  \stemUp
  \once\stemDown \musictwo
}

thirdvoice = \relative {
  \key bes \major
  % default
  \musicthree
  % voices 1 3 2
  \voiceTwo
  \musicthree
  % voices 1 4 2
  \musicthree
  % manual up/down
  \stemUp
  \once\stemDown \musicthree |
}


\new Staff <<
  \firstvoice
  \secondvoice
  \thirdvoice
>>