3.1.3+4 Output file names and multiple output files

   LilyPond creates one output file for each \book block.

   If there is no explicit \book block in the input file, LilyPond
   implicitly treats the whole file as a single \book block, see Section
   3.1.5 [File structure], page 426.

   By default LilyPond names the output file using the input filename and
   if necessary suffixes it with an increasing number - i.e. if an output
   file with the same name has already been created during the run.

   It is possible to override both the output filename and the suffix
   appended to the basic filename in the \paper block of each \book:
\book {
  \paper {
    output-filename = "my special output"
    output-suffix = "menuetto"
  }
}

   The result is an output file named "my special output-menuetto.pdf".

   Note: Predefined \paper variables must be placed before the
   output-filename and output-suffix assignements, e.g.
bigMargin = \paper { top-margin = 10 \cm }
\book {
  \paper {
    \bigMargin
    output-filename = "filename after bigMargin"
  }
  \relative { c }
}