+@lilypond[quote,verbatim,ragged-right]
+<<
+ \new Staff \relative c'' {
+ \set Staff.instrumentName = #"Soprano"
+ c4 c
+ }
+ \new Staff \relative c' {
+ \set instrumentName = #"Alto" % Wrong!
+ d4 d
+ }
+>>
+@end lilypond
+
+Remember the default context name is Voice, so the second
+@code{\set} command set the property @code{instrumentName} in the
+Voice context to @qq{Alto}, but as LilyPond does not look
+for any such property in the @code{Voice} context, no
+further action took place. This is not an error, and no error
+message is logged in the log file.
+
+Similarly, if the property name is mis-spelt no error message
+is produced, and clearly the expected action cannot be performed.
+If fact, you can set any (fictitious) @q{property} using any
+name you like in any context that exists by using the
+@code{\set} command. But if the name is not
+known to LilyPond it will not cause any action to be taken.
+This is one of the reasons why it is highly recommended to
+use a context-sensitive editor with syntax highlighting for
+editing LilyPond files, such as Vim, Jedit, ConTEXT or Emacs,
+since unknown property names will be highlighted differently.
+
+The @code{instrumentName} property will take effect only
+if it is set in the @code{Staff} context, but
+some properties can be set in more than one context.
+For example, the property @code{extraNatural} is by
+default set to ##t (true) for all staves.
+If it is set to ##f (false) in one particular @code{Staff}
+context it applies just to the accidentals on that staff.
+If it is set to false in the @code{Score} context
+it applies to all staves.
+
+So this turns off extra naturals in one staff:
+
+@lilypond[quote,verbatim,ragged-right]
+<<
+ \new Staff \relative c'' {
+ ais4 aes
+ }
+ \new Staff \relative c'' {
+ \set Staff.extraNatural = ##f
+ ais4 aes
+ }
+>>
+@end lilypond
+
+@noindent
+and this turns them off in all staves:
+
+@lilypond[quote,verbatim,ragged-right]
+<<
+ \new Staff \relative c'' {
+ ais4 aes
+ }
+ \new Staff \relative c'' {
+ \set Score.extraNatural = ##f
+ ais4 aes
+ }
+>>
+@end lilypond
+
+The value of every property set in this way can be reset
+to its original value with the @code{\unset} command.
+
+The @code{\set} and @code{\unset} commands can appear anywhere
+in the input file and will take effect from the time they are
+encountered until the end of the score or until the property is
+@code{\set} or @code{\unset} again. Let's try changing the
+font size, which affects the size of the note heads (among
+other things) several times. The change is from the default
+value, not the current value.
+
+@lilypond[quote,verbatim,ragged-right,relative=1,fragment]
+c4
+% make note heads smaller
+\set fontSize = #-4
+d e
+% make note heads larger
+\set fontSize = #2.5
+f g
+% return to original size
+\unset fontSize
+a b
+@end lilypond
+
+We have now seen how to set the values of several different
+types of property. Note that integers and numbers are alway
+preceded by a hash sign, @code{#}, while a true or false value
+is specified by ##t and ##f, with two hash signs. A text
+property should be enclosed in double quotation signs, as above,
+although we shall see later that text can actually be specified
+in a much more general way by using the very powerful
+@code{markup} command.
+
+
+@funindex \with
+
+Context properties may also be set at the time the context is
+created. Sometimes this is a clearer way of specifying a
+property value if it is to remain fixed for the duration of
+the context. When a context is created with a @code{\new}
+command it may be followed immediately by a
+@code{\with @{ .. @}} block in which the property values are
+set. For example, if we wish to suppress the printing of
+extra naturals for the duration of a staff we would write:
+
+@example
+\new Staff \with @{ extraNatural = ##f @}
+@end example
+
+@noindent
+like this:
+
+@lilypond[quote,verbatim,ragged-right]
+<<
+ \new Staff
+ \relative c'' {
+ gis ges aes ais
+ }
+ \new Staff \with { extraNatural = ##f }
+ \relative c'' {
+ gis ges aes ais
+ }
+>>
+@end lilypond
+
+In effect this overrides the default value of the property. It
+may still be changed dynamically using @code{\set} and returned
+to its (new) default value with @code{\unset}.
+
+@node Adding and removing engravers
+@subsection Adding and removing engravers
+
+@cindex Engravers, adding
+@cindex Engravers, removing
+
+@funindex \consists
+@funindex \remove
+
+We have seen that contexts each contain several engravers, each
+of which is responsible for producing a particular part of the
+output, like bar lines, staves, note heads, stems, etc. If an
+engraver is removed from a context it can no longer produce its
+output. This is a crude way of modifying the output, but it
+can sometimes be useful.
+
+@subsubheading Changing a single context
+
+To remove an engraver from a single context we use the
+@code{\with} command placed immediately after the context creation
+command, as in the previous section.
+
+As an
+illustration let's repeat an example from the previous
+section with the staff lines removed. Remember that the
+staff lines are produced by the Staff_symbol_engraver.
+
+@lilypond[quote,verbatim,ragged-right]
+\new Staff \with {
+ \remove Staff_symbol_engraver
+}
+\relative c' {
+ c4
+ \set fontSize = #-4 % make note heads smaller
+ d e
+ \set fontSize = #2.5 % make note heads larger
+ f g
+ \unset fontSize % return to original size
+ a b