\version "2.19.44"

\score {
\new PianoStaff
<<
  \new Lyrics = "buttonsII" \with {
    \override VerticalAxisGroup.staff-affinity = #DOWN
  }
  \new Lyrics = "buttonsI" \with {
    \override VerticalAxisGroup.staff-affinity = #DOWN
  }
  \new Voice = "melody" \fixed c'
  {
    \set midiInstrument = #"accordion"
    \key f \major
    \time 2/4
    \repeat unfold 60 { <a c'>4 }
  }
  \new Lyrics = "lyricsI"   {}

  \context Lyrics = "buttonsII" {
    \lyricsto "melody" {
      _ _ _ _ _ _ _ _ _ _
      "4"
%       % this works ok
%       \repeat unfold 60 { "4" }
    }
  }
  \context Lyrics = "buttonsI" {
    \lyricsto "melody" {
    \repeat unfold 60 { "3" }
    }
  }

  \context Lyrics = "lyricsI" {
    \lyricsto "melody" {
      _ _ _ _ _ _ _ _ _ _
      \repeat unfold 50 { ac }
    }
  }

  \new FiguredBass {
    \figuremode {
      \repeat unfold 30 {<1>4 <2>}
    }
  }
>>
}