\version "2.17.24"

singer = \relative c' {
  \repeat volta 2 { f4 g( a) r }
  c1
}

\addQuote "echo" { \singer }

continuo = {
  \set Score.quotedEventTypes = #'(note-event rest-event)
  \quoteDuring "echo" {
    \repeat volta 2 { s1 }
    s1
  }
}

\markup { Printed output }
\score {
  <<
    \new Staff { \singer }
    \new Staff { \new Voice { \continuo } }
  >>
  \layout { }
}

\markup { With unfoldRepeats for MIDI }
\score {
  \unfoldRepeats
  <<
    \new Staff { \singer }
    \new Staff { \new Voice { \continuo } }
  >>
  \layout { }
  \midi { }
}