Text markup: vspace with negative number

[Jethro Van Thuyne]

I'm trying to reduce the line width in a custom header template,
having several lines combined in \center-column. I tried using
the \vspace command, which seems the only thing in the docs
slightly related to line height, but it doesn't seem to handle
negative numbers.

bookTitleMarkup = \markup
  {
  \fill-line
    {   
    \center-column
      {   
      \fontsize #4.5 \fromproperty #'header:title
      \fontsize #-3 \fromproperty #'header:copyMusic
      \vspace #-2
      \fontsize #-3 \fromproperty #'header:copyLyric
      }   
    }   
  }   

Any way to set the line height to a smaller number than the
default value in \center-column?

Jethro