\layout {
  \context {
    \Score
    \remove "Timing_translator"
  }
  \context {
    \Staff
    \consists "Timing_translator"
  }
}

<<
  \new Staff {
    \scaleDurations 8/5 {
      \time 6/8
      \set Timing.measureLength = #(ly:make-moment 6/5)
      b8 b b b b b
      \time 2/4
      \set Timing.measureLength = #(ly:make-moment 4/5)
      b4 b
    }
  }
  \new Staff {
    \clef bass
    \time 2/4
    c2 d e f
  }
>>