spacing between lines of a lead sheet?

[iain duncan]

I've been trying to change various variables to no avail. If anyone can
point me at the right way to increase space between the lines of a lead
sheet given the template below ( which may well be all mucked up ... )
that would be wonderful. =)

Thanks
iain


\version "2.10.10"


\header {
    title = "Song Title"
}

\paper {
  #(define dump-extents #t)
  
  indent = 0\mm
  between-system-space = 4.5\cm
  between-system-padding = #4 
  
}

melody = \relative c' {
   \clef treble
   \key c \major
   \time 4/4

   f4 e8[ c] d4 g | a2 ~ a2 | f4 e8[ c] d4 g | a2 ~ a2 | \break
   f4 e8[ c] d4 g | a2 ~ a2 | f4 e8[ c] d4 g | a2 ~ a2 | \break
   f4 e8[ c] d4 g | a2 ~ a2 | f4 e8[ c] d4 g | a2 ~ a2 | \break
}

harmonies = \chordmode {
   c2:m f2:min7 d1:dim | c2:m f2:min7 d1:dim   \break
   c2:m f2:min7 d1:dim | c2:m f2:min7 d1:dim   \break
}

\score {
   <<

  \new ChordNames {
       \set chordChanges = ##t
       \harmonies
   }
   \new Staff \melody
   >>

   \layout {
        \context { \Staff
            \override VerticalAxisGroup #'minimum-Y-extent = #'(-6 . 6)
        }
   }

}