+As you can see, writing a melody in the treble clef involves a lot
+of quote @code{'} marks. Consider this fragment from Mozart:
+
+@lilypond[verbatim,quote,ragged-right]
+{
+ \key a \major
+ \time 6/8
+ cis''8. d''16 cis''8 e''4 e''8
+ b'8. cis''16 b'8 d''4 d''8
+}
+@end lilypond
+
+All these quotes makes the input less readable and it is a source
+of errors. With @code{\relative}, the previous example is much
+easier to read:
+
+@lilypond[verbatim,quote,ragged-right]
+\relative c'' {
+ \key a \major
+ \time 6/8
+ cis8. d16 cis8 e4 e8
+ b8. cis16 b8 d4 d8
+}
+@end lilypond
+
+If you make a mistake with an octave mark (@code{'} or @code{,})
+while working in @code{\relative} mode, it is very obvious -- many
+notes will be in the wrong octave. When working in absolute mode,
+a single mistake will not be as visible, and will not be as easy
+to find.
+
+However, absolute mode is useful for music which has large
+intervals, and is extremely useful for computer-generated LilyPond
+files.
+
+
+@node Organizing pieces with variables
+@subsection Organizing pieces with variables
+
+When all of the elements discussed earlier are combined to produce
+larger files, the music expressions get a lot bigger. In
+polyphonic music with many staves, the input files can become very
+confusing. We can reduce this confusion by using
+@emph{variables}.
+
+With variables (also known as identifiers or macros), we can break
+up complex music expressions. A variable is assigned as
+follows: