In @LaTeX{}, define @code{\betweenLilyPondSystem} in such a way that
inclusion of other systems is terminated once the required number of
-systems are included. Since @code{\betweenLilypondSystem} is first
+systems are included. Since @code{\betweenLilyPondSystem} is first
called @emph{after} the first system, including only the first system
is trivial.