Lilypond: Can't create title for song

Question

The following displays only the book title. I want a separate title for each score. It shows the opus and piece, but not the title for that score. What am I doing wrong? I'm basing this on Creating titles headers and footers.

\version "2.18.2"
\book {
    \header {
        title = "book title"
    }
    \score {
        \header {
            title = "song title is missing"
            subtitle = "subtitle is missing"
            opus = "opus"
            piece = "yo"
        }
        \new Staff {
            \key f \major
            \time 6/4
            \clef treble
        } % Staff
    } % score
} % book

Answer 1

You could force LilyPond to display all titles like with this \paper block:

\version "2.18.2"
\book {
\paper {print-all-headers = ##t}
    \header {
        title = "book title"
    }
    \score {
        \header {
            title = "song title is missing"
            subtitle = "subtitle is missing"
            opus = "opus"
            piece = "yo"
        }
        \new Staff {
            \key f \major
            \time 6/4
            \clef treble
        } % Staff
    } % score
} % book

You can see it here on lilybin.com.

I have no idea why the default behavior is not to display the title, but fortunately you can always change the setting to what you like most.

Answer 2

bookpart is another way, though if you want a one-off title and the part title to be in the title field then a leading title page and to use title for what I've placed in subtitle for each bookpart may be necessary:

\version "2.18.2"
\header {
    title = "book title"
}
\book {
    \bookpart {
        \header {
            subtitle = "part1"
            opus = "opus"
            piece = "yo"
        }
        \score {
            \new Staff {
                \key f \major
                \time 6/4
                \clef treble
            }
        }
    }
    \bookpart {
        \header {
            subtitle = "part2"
            opus = "opus"
            piece = "yo"
        }
        \score {
            \new Staff {
                \key f \major
                \time 6/4
                \clef treble
            }
        }
    }
}

Answer 3

From Lilypond's manual:

4.1.6 Miscellaneous \paper variables

• print-all-headers

...this will print all headers for each \score in the output. Normally only the piece and opus header variables are printed. Default: #f.

3.2.1 Titles explained:

...only piece and opus fields are printed by default in Score Titles unless the \paper variable, print-all-headers, is set to #t.

So, for an example that includes a book header and multiple score headers, that would look like this:

\book {

 \paper {
  print-all-headers = ##t
 }

 \header {
  title = "Title for book"
 }
 
 \score {
  %...music here...
  \header {
   title = "Title for first score"
  }
 }
 
 \score {
  %...music here...
  \header {
   title = "Title for second score"
  }
 }

}

That should do the trick.