\version "2.16.1"

fontCheck =
#(make-engraver
  (acknowledgers
   ((text-interface engraver grob source-engraver)
    (ly:message "saw ~A coming from ~A" grob source-engraver)
    (ly:message "'text=~A" (markup->string (ly:grob-property grob 'text "???")))
    (let ((abs-font-size (ly:grob-property grob 'abs-font-size)))
      (if (and (number? abs-font-size)(> abs-font-size 0))
          (ly:grob-set-property! grob 'text (markup #:abs-fontsize abs-font-size (ly:grob-property grob 'text "???")))
          ))
    ))
  )

\layout {
  \context {
    \Score
    \consists #fontCheck
    \override TextScript #'abs-font-size = #24
    \override LyricText #'abs-font-size = #24
    \override InstrumentName #'abs-font-size = #24
    \override BarNumber #'abs-font-size = #24
  }
}

\new Staff \with {
  instrumentName = "Melodie"
  shortInstrumentName = "Mel"
} \new Voice { \repeat unfold 25 \relative c'' {
  bes4^"Hallo" a c b
} } \addlyrics { B A C H }