-are also used to set PDF metadata (the information displayed by PDF readers
-as the @code{properties} of the PDF file). For example, setting the
-@code{title} property of the @code{header} block @q{Symphony I} will also give
-this title to the PDF document.
-
-@example
- @code{\header@{}
- @code{title = "Symphony I"}
- @code{@}}
+are also used to set metadata for output files. For example, with PDF
+files, this metadata could be displayed by PDF readers as the
+@code{properties} of the PDF file. For each type of output file, only the
+@code{\header} definitions of blocks that define separate files of that
+type, and blocks higher in the block hierarchy, will be consulted.
+Therefore, for PDF files, only the @code{\book} level and the top level
+@code{\header} definitions affect the document-wide PDF metadata, whereas
+for MIDI files, all headers above or at the @code{\score} level are used.
+
+For example, setting the @code{title} property of the @code{header} block
+to @q{Symphony I} will also give this title to the PDF document, and use
+it as the sequence name of the MIDI file.
+
+@example
+\header@{
+ title = "Symphony I"
+@}