\version "2.18.2"

\parallelMusic #'(voiceA voiceB) \relative c'' {
  <gis cis eis gis>1	|
  eis,1 		|
  \set Staff . accidentalGrouping = #'voice
  <gis' cis eis gis>1	|
  eis, 			|
}
      
<< \voiceA \\ \voiceB >>