-Manually marked footnotes take an additional first markup argument
-@var{mark} for making the reference mark. In contrast to automatically
-generated footnote marks, they will not appear before the @var{footnote}
-markup at the bottom of the page: establishing the visual connection is
-left to the user. LilyPond will only make sure that the corresponding
-markup appears on the bottom of the same page.
+@warning {When footnotes are attached to several musical elements at
+the same musical moment, as they are in the example above, the
+footnotes are numbered from the higher to the lower elements as they
+appear in the printed output, not in the order in which they are
+written in the input stream.}
+
+Layout objects like clefs and key-change signatures are mostly caused
+as a consequence of changed properties rather than actual events.
+Others, like bar lines and bar numbers, are a direct consequence of
+timing. For this reason, footnotes on such objects have to be based
+on their musical timing. Time-based footnotes are also preferable
+when marking features like stems and beams on @emph{chords}: while
+such per-chord features are nominally assigned to @emph{one} event
+inside the chord, relying on a particular choice would be imprudent.
+
+The layout object in question must always be explicitly specified
+for time-based footnotes, and the appropriate context must be
+specified if the grob is created in a context other than the bottom
+context.
+
+@lilypond[quote,verbatim,papersize=a8landscape]
+\book {
+ \header { tagline = ##f }
+ \relative c'' {
+ r1 |
+ \footnote #'(-0.5 . -1) "Meter change" Staff.TimeSignature
+ \time 3/4
+ \footnote #'(1 . -1) "Chord stem" Stem
+ <c e g>4 q q
+ \footnote #'(-0.5 . 1) "Bar line" Staff.BarLine
+ q q
+ \footnote #'(0.5 . -1) "Key change" Staff.KeySignature
+ \key c \minor
+ q
+ }
+}
+@end lilypond