One simple way to obtain an A5 booklet is to run ly2dvi and dvips
the normal way to produce an A4 score, then run 'mpage -2' or
'psnup -2' on the postscript file to get the desired A5 layout.
The problem is that the music fonts don't scale perfectly which
might give some fuzzy lines in the output.
The better solution is to include something like the following
in your mudela file:
\include "paper13.ly"
\score{
...
\paper{
\paper_thirteen % Sets the staff size
linewidth = 130.\mm; % Width of the music
textheight = 190.\mm; % height of the music
pagesize = "a5" % page format
...
}
...
}
I haven't actually tried the pagesize macro myself and don't have
Lilypond installed here right now, but from the source code of
ly2dvi, it looks as if it should work. There is also a paper11.ly
file with corresponding macro \paper_eleven that gives even
smaller staffs.
/Mats