Kneed Beams in Multiple Voices

[Derek Klinge]

List,

 I am trying to typeset a Bach Fugue. It would be much prettier if I could have kneed beams in a polyphonic texture. I cannot figure out how to have kneed beam in \voiceTwo

\relative c'' {

\new PianoStaff <<

  \new Staff = "up"  { << { g4 ges f fes } \\ {bes,8 c16 des ees8 \change Staff = "down" ees,^] aes \change Staff = "up" bes16 c des4 } >> }

  \new Staff = "down" { \clef bass des,16 f ees des ces des ees8 ~ ees16 des c bes ces bes aes }

>>

}

Thanks,

Derek