\new PianoStaff <<
      \new Staff <<
         \new Voice \relative c'' {
             \stemUp \clef treble \key c \major \time 4/4
             b1 c
             }
         \new Voice \relative c'' {
             \stemDown
              g1 g
              }
            >>
     \new Staff <<
         \new Voice \relative c' {
             \stemUp \clef bass \key c \major \time 4/4
             d1 e
             }
         \new Voice \relative c' {
             \stemDown
             g1 c, \bar "||"
             }
         >>
    >>