\version "2.8.0"
\score {
<<
\new ChoirStaff <<
\new Staff <<
\new Voice = "BeamTestStaff" {  
 \clef "treble"
 \time 4/4
 e''8 g''8 e''8 g''8
<<
{ \voiceOne
a''8 b''8}\new Voice
{ \voiceTwo
a''8 a''8}
>>
\oneVoice
< aes'' c'''>8.< aes'' d'''>16  |
< g'' e'''>8 g''8\times 2/3 {  a''8 (  [  b''8 )  ]  c'''8 }  c'''4 b''4 \bar "|."
}
\new Lyrics \lyricsto "BeamTestStaff" {  la la la la la la la la la la la la }>>
>>
>>
}