Vertical spacing is automatically set so that the layout of a score is neither too cramped or loose. Changing the distance between systems, however, is easy to do. You may want to move systems closer together so that more can fit on the page, for example.
Four keys are available for fine-tuned control, but you may find
that you can get the spacing you want with changes to just one or two. The
output of this snippet is the result of a change to a single key, padding.
You may want to experiment with the commented-out line below it, which
contains the default values for system-system-spacing and shows the
syntax to use for changes in groups. Numbers represent distances in staff-spaces.
For more details you should consult Section 4.1 of the Notation Reference.