[itsme]

In fact, different line spacings exist: 
- the space between a lyrics line and the according chords 
- the space between a lyrics line and the chords of the next lyrics line (if it has chords)
- the space between a lyrics line and the next lyrics line (if it doesn't have chords)

I'm not sure if it is worth the effort to allow setting them independently. 
Nevertheless it might make sense to have a lyrics line and the according chords closer together.