+@example
+\footnote @var{mark} @var{offset} @var{grob-name} @var{footnote}
+@var{music}
+@end example
+
+The elements are as follows:
+
+@table @var
+@item mark
+is a markup or string specifying the footnote mark which is used for
+both marking the reference point as well as the footnote itself at the
+bottom of the page. It can be omitted (or equivalently replaced with
+@code{\default}) in which case a number in sequence will be generated.
+@item offset
+is a number pair such as @samp{#(2 . 1)} specifying the X and Y offset
+from the reference point where the mark will be placed.
+@item grob-name
+specifies a type of grob to mark (like @samp{#'Flag}). If it is given,
+the respective grob will be used as a reference point even in case that
+its @q{cause} is not the referenced @var{music} itself but a grob
+created from it. It can be omitted (or replaced with @code{\default}),
+and then only a directly created grob will be annotated.
+@item footnote
+This markup or string specifies the footnote text to use at the bottom
+of the page.
+@item music
+This is the item, a music event or chord constituent or post-event, that
+is being annotated. While it cannot be omitted, it @emph{can} be
+replaced by @code{\default} in which case the footnote is not attached
+to a music expression in particular, but rather to a moment of time. It
+is mandatory in this case to use the @var{grob-name} argument for
+selecting an affected grob type, like @samp{#'TimeSignature}.
+@end table
+
+Like with @code{\tweak}, if your @code{\footnote} is applied to a
+post-event or articulation, it will itself have to be preceded with
+@code{-} to make the parser attach the result to the preceding note or
+rest.