Forcing horizontal space between successive notes

[David Sumbler]

I have various clunky workarounds for this problem, but I am still
wondering whether there isn't a neater way.

How can one force additional space between 2 successive musical moments
in a score, without affecting the spacing algorithm to the left and
right?  This is occasionally desirable, for instance to leave
horizontal space for some textual instruction or narration.

I have experimented with all sorts of parameters for various items such
as PaperColumn, VerticalAlignment, SpacingSpanner and others, but so
far without any success.

David