@end itemize
+If you are entering music from an existing score (ie typesetting a
+piece of public domain music),
+
+@itemize @bullet
+
+@item Enter one manuscript (the physical copy) line at a time, and
+check each line when you finish it. You may use the
+@code{showLastLength} command to speed up processing -- see
+@ref{Skipping corrected music}.
+
+@item Define @code{mBreak = @{ \break @}} and insert @code{\mBreak}
+in the input file whenever the manuscript has a line break. This
+makes it much easier to compare the LilyPond music to the original
+music. When you are finished proofreading your score, you may
+define @code{mBreak = @{ @}} to remove all those line breaks. This
+will allow LilyPond to place line breaks wherever it feels are
+best.
+
+@end itemize
+
@node Extending the templates
@section Extending the templates
@end example
@noindent
-Remember that you can use any names you like.
+Remember that you can use almost any name you like. The
+limitations on identifier names are detailed in
+@ref{File structure}.
When writing a @code{\score} section, or when reading
one, just take it slowly and carefully. Start with
you find the error, but in many cases you need to do some
investigation to determine the source of the problem.
-The most powerful tool for this purpose is the
-comment (@code{%} and @code{%@{ ... %@}}). If you don't
+The most powerful tools for this purpose are the
+single line comment (indicated by @code{%}) and the block
+comment (indicated by @code{%@{ ... %@}}). If you don't
know where a problem is, start commenting out huge portions
of your input file. After you comment out a section, try
compiling the file again. If it works, then the problem