\version "2.10.10"

harmony = \context ChordNames {
  \chordmode {
    c1 |
    g |
  }
}

<< \harmony
   \new PianoStaff <<
     \new Staff = "upper" {
       \relative c' {
         c4 c c c
         d d d d
       }
     }
     \addlyrics {
       \repeat unfold 4 \skip 1
       la la la la
     }
     \new Staff = "lower" {
       \relative c' {
          c4 c c c
       }
     }
 >>
>>