+@node The single prefix
+@unnumberedsubsubsec The @code{@bs{}single} prefix
+
+@funindex \single
+@cindex tweak, generated from override
+
+Suppose we wanted to emphasize particular note heads by coloring them
+red and increasing their size, and to make it easy suppose also we
+have defined a function to do this:
+
+@lilypond[quote,verbatim]
+emphNoteHead = {
+ \override NoteHead.color = #red
+ \override NoteHead.font-size = 2
+}
+\relative {
+ c''4 a \once \emphNoteHead f d |
+}
+@end lilypond
+
+The @code{\once} prefix works fine to emphasize single notes or
+complete chords, but it cannot be used to emphasize a single note
+@emph{within} a chord. Earlier we have seen how @code{\tweak} can
+be used to do this, see
+@ref{The tweak command,,The @code{@bs{}tweak} command}. But
+@code{\tweak} cannot be used with a function; that's where
+@code{\single} comes in:
+
+@lilypond[quote,verbatim]
+emphNoteHead = {
+ \override NoteHead.color = #red
+ \override NoteHead.font-size = 2
+}
+\relative {
+ <c'' a \single \emphNoteHead f d>4
+}
+@end lilypond
+
+In summary, @code{\single} converts overrides into tweaks so when
+there are several objects at the same point in musical time (like
+noteheads in a chord), @code{\single} will only affect a single one,
+the one generated by the immediately following music expression, in
+contrast to @code{\once} which will affect all of those objects.
+
+By using @code{\single} in this way any shorthand function
+containing just overrides may be applied to individual notes in a
+chord. However, @code{\single} does not convert @code{\revert},
+@code{\set} or @code{\unset} into tweaks.
+
+@seealso
+Learning Manual:
+@ref{The tweak command,,The @code{@bs{}tweak} command},
+@ref{Using variables for layout adjustments}.
+