How to really center a text above a note?

[Wilbert Berendsen]

Hi,

There must be a way to really center a simple text above a note. But these two 
lines center the text above the *left* side of the note:

{  c'4-\markup\center-align text  }

{
  \once \override TextScript #'self-alignment-X = #CENTER
  c'4-"text"
}

How can I center a text or markup above the *center* of the note/chord?

tia,
Wilbert Berendsen

-- 
Frescobaldi, LilyPond editor for KDE: http://www.frescobaldi.org/