+<<
+ {
+ \once \override Stem #'transparent = ##t
+ \once \override Stem #'length = #8
+ b8~ b8\noBeam
+ }
+\\
+ { b[ g8] }
+>>
+@end lilypond
+
+@subheading Simulating a fermata
+
+@cindex stencil property, use of
+@cindex fermata, implementing in MIDI
+
+For outside-staff objects it is usually better to override the
+object's @code{stencil} property rather than its @code{transparent}
+property when you wish to remove it from the printed output.
+Setting the @code{stencil} property of an object to @code{#f} will
+remove that object entirely from the printed output. This means it
+has no effect on the placement of other objects placed relative to
+it.
+
+For example, if we wished to change the metronome setting in order
+to simulate a fermata in the MIDI output we would not want the
+metronome markings to appear in the printed output, and we would
+not want it to influence the spacing between the two systems or
+the spacing of the notes on the staff. So setting its
+@code{stencil} property to @code{#f} would be the best way.
+We show here the effect of the two methods:
+
+@lilypond[quote,verbatim,ragged-right]
+\score {
+ \relative c'' {
+ % Visible tempo marking
+ \tempo 4=120
+ a4 a a
+ \once \override Score.MetronomeMark #'transparent = ##t
+ % Invisible tempo marking to lengthen fermata note in MIDI
+ \tempo 4=80
+ a\fermata
+ \once \override Score.MetronomeMark #'stencil = ##f
+ % Invisible tempo marking to restore tempo in MIDI
+ \tempo 4=120
+ a a a a
+ }
+ \layout { }
+ \midi { }
+}
+@end lilypond
+
+@noindent
+Both methods remove the metronome mark from the printed output,
+and both affect the MIDI timing as required, but the first
+(transparent) metronome mark still influences the note spacing
+while the second (with no stencil) does not.
+
+@node Using variables for tweaks
+@subsection Using variables for tweaks
+
+Override commands are often long and tedious to type, and they
+have to be absolutely correct. If the same overrides are to be
+used many times it may be worth defining variables to hold them.
+Suppose we wish to emphasize certain words in lyrics by printing
+them in bold italics. The @code{\italic} and @code{\bold}
+commands do not work within lyrics so we must instead use the
+following @code{\override} and @code{\revert} commands:
+
+@example
+@code{\override Lyrics . LyricText #'font-shape = #'italic}
+@code{\override Lyrics . LyricText #'font-series = #'bold}
+
+@code{\revert Lyrics . LyricText #'font-shape}
+@code{\revert Lyrics . LyricText #'font-series}
+@end example
+
+These would be extremely tedious to enter if there were many words
+requiring emphasis. So instead we define these as two variables,
+and use them as follows:
+
+@lilypond[quote,verbatim]
+emph = {
+ \override Lyrics . LyricText #'font-shape = #'italic
+ \override Lyrics . LyricText #'font-series = #'bold
+}
+norm = {
+ \revert Lyrics . LyricText #'font-shape
+ \revert Lyrics . LyricText #'font-series
+}
+
+global = { \time 4/4 \partial 4 \key c \major}
+SopMusic = \relative c' { c4 | e4. e8 g4 g | a a g }
+AltoMusic = \relative c' { c4 | c4. c8 e4 e | f f e }
+TenorMusic = \relative c { e4 | g4. g8 c4. b8 | a8 b c d e4 }
+BassMusic = \relative c { c4 | c4. c8 c4 c | f8 g a b c4 }
+VerseOne = \lyrics { E -- | ter -- nal \emph Fa -- ther, \norm | strong to save, }
+VerseTwo = \lyricmode { O | \emph Christ, \norm whose voice the | wa -- ters heard, }
+VerseThree = \lyricmode { O | \emph Ho -- ly Spi -- rit, \norm | who didst brood }
+VerseFour = \lyricmode { O | \emph Tri -- ni -- ty \norm of | love and pow'r }
+
+\score {
+ \new ChoirStaff <<
+ \new Staff <<
+ \clef "treble"
+ \new Voice = "Sop" { \voiceOne \global \SopMusic }
+ \new Voice = "Alto" { \voiceTwo \AltoMusic }
+ \new Lyrics \lyricsto "Sop" { \VerseOne }
+ \new Lyrics \lyricsto "Sop" { \VerseTwo }
+ \new Lyrics \lyricsto "Sop" { \VerseThree }
+ \new Lyrics \lyricsto "Sop" { \VerseFour }
+ >>
+ \new Staff <<
+ \clef "bass"
+ \new Voice = "Tenor" { \voiceOne \TenorMusic }
+ \new Voice = "Bass" { \voiceTwo \BassMusic }
+ >>
+ >>
+}