I have had several requests on how to change the score spacing and line feeds in my music program HARMONY. Although this is possible, details are buried in the reference manual which is included in the distribution as MAN321.DOC.

In summary, you have currently have to use the Edit Voice Text facility to insert spacing commands directly into the text version of the music (VOICE 1 only).

Commands available are

@F to force a new line on the score
@nn to insert nn spacing units (basically a note's width)
@Pnn to insert nn Pixels of space
@Snn to adjust the default spacing in pixels.
(nn can in this case be negative, to reduce the default spacing)

I will try and add these to the menus in the next version, to make it easier.

Note that HARMONY does also implement the Newline character (Backslash) when importing abc files.

HARMONY is available from my site :
http://www.greenhedges.com