allow creation of multiple output files

[tymbalodeon]

For some charts, it make sense to have a more detailed transcription of the complete melody with cue parts showing important aspects of the arrangement, but at the same time have a simpler form chart that just shows the sections with chords and number of bars.

This can be done using "\book" blocks in LilyPond.

See: https://lilypond.org/doc/v2.23/Documentation/notation/output-file-names