Changing spacing in a piece?

[Alasdair McAndrew]

I have enlarged the spacing between systems (for readability) with

\paper{
 system-system-spacing = #'((basic-distance . 15) (padding . 5))
}

But there's one part of this score which consists of several lines 
of just one voice on one staff, and for which this enlarged 
spacing is unnecessary.

How can I override my spacing for this one section?  Or more 
generally, how can I adjust the spacing for different parts of the 
score?

Thanks,
Alasdair

--
Alasdair McAndrew
http://numbersandshapes.net