\version "2.19.49"

firstVoice  = \relative c' { \aikenHeads c4 d e f g a b c }
sameVoice   = \relative c' { \aikenHeads c4 d e f g a b c }
thirdVoice  = \relative c' { \aikenHeads a4 b c d e f g a }
fourthVoice = \relative c' { \aikenHeads c4 b e d g f b a }

<<
  \new Staff \with { instrumentName = "firstVoice"  } \firstVoice
  \new Staff \with { instrumentName = "sameVoice"   } \sameVoice
  \new Staff \with { instrumentName = "thirdVoice"  } \thirdVoice
  \new Staff \with { instrumentName = "fourthVoice" } \fourthVoice
  \new Staff \with { instrumentName = "unison"      } \partcombine #'(2 . 12) \firstVoice \sameVoice
  \new Staff \with { instrumentName = "thirds"      } \partcombine #'(2 . 12) \firstVoice \thirdVoice
  \new Staff \with { instrumentName = "mix"         } \partcombine #'(2 . 12) \firstVoice \fourthVoice
>>