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<p>
<a name="Modifying-context-plug-ins"></a>
<a name="Modifying-context-plug_002dins"></a>
Next: <a rel="next" accesskey="n" href="Changing-context-default-settings.html#Changing-context-default-settings">Changing context default settings</a>,
Previous: <a rel="previous" accesskey="p" href="Creating-contexts.html#Creating-contexts">Creating contexts</a>,
Up: <a rel="up" accesskey="u" href="Interpretation-contexts.html#Interpretation-contexts">Interpretation contexts</a>
<hr>
</div>
<h4 class="subsection">5.1.3 Modifying context plug-ins</h4>
<!-- TODO Should this be Modifying engravers or Modifying contexts? -->
<p>Notation contexts (like <code>Score</code> and <code>Staff</code>) not only
store properties,
they also contain plug-ins called ‘engravers’ that create notation
elements. For example, the <code>Voice</code> context contains a
<code>Note_head_engraver</code> and the <code>Staff</code> context contains a
<code>Key_signature_engraver</code>.
<p>For a full a description of each plug-in, see
<a name="index-Engravers-and-Performers-2629"></a><a href="../lilypond-internals/Engravers-and-Performers.html#Engravers-and-Performers">Engravers and Performers</a>.
Every context described in
<a name="index-Contexts-2630"></a><a href="../lilypond-internals/Contexts.html#Contexts">Contexts</a>
lists the engravers used for that context.
<p>It can be useful to shuffle around these plug-ins. This is done by
starting a new context with <code>\new</code> or <code>\context</code>, and
modifying it,
<p><a name="index-g_t_005cwith-2631"></a><a name="index-g_t_005cwith-2632"></a>
<pre class="example">\new <var>context</var> \with {
\consists ...
\consists ...
\remove ...
\remove ...
<em>etc.</em>
}
{
<em>..music..</em>
}
</pre>
<p class="noindent">where the <small class="dots">...</small> should be the name of an engraver. Here is a simple
example which removes <code>Time_signature_engraver</code> and
<code>Clef_engraver</code> from a <code>Staff</code> context,
<blockquote>
<pre class="verbatim">
<<
\new Staff {
f2 g
}
\new Staff \with {
\remove "Time_signature_engraver"
\remove "Clef_engraver"
} {
f2 g2
}
>>
</pre>
<p>
<a href="../5f/lily-208361c9.ly">
<img align="middle"
border="0" src="../5f/lily-208361c9.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p>In the second staff there are no time signature or clef symbols. This
is a rather crude method of making objects disappear since it will affect
the entire staff. This method also influences the spacing, which may or
may not be desirable. More sophisticated methods of blanking objects
are shown in <a name="index-Visibility-and-color-of-objects-2633"></a><a href="../lilypond-learning/Visibility-and-color-of-objects.html#Visibility-and-color-of-objects">Visibility and color of objects</a>.
<p>The next example shows a practical application. Bar lines and time
signatures are normally synchronized across the score. This is done
by the <code>Timing_translator</code> and <code>Default_bar_line_engraver</code>.
This plug-in keeps an administration of time signature, location
within the measure, etc. By moving these engraver from <code>Score</code> to
<code>Staff</code> context, we can have a score where each staff has its own
time signature.
<p><a name="index-polymetric-scores-2634"></a><a name="index-Time-signatures_002c-multiple-2635"></a>
<blockquote>
<pre class="verbatim">
\new Score \with {
\remove "Timing_translator"
\remove "Default_bar_line_engraver"
} <<
\new Staff \with {
\consists "Timing_translator"
\consists "Default_bar_line_engraver"
} {
\time 3/4
c4 c c c c c
}
\new Staff \with {
\consists "Timing_translator"
\consists "Default_bar_line_engraver"
} {
\time 2/4
c4 c c c c c
}
>>
</pre>
<p>
<a href="../3b/lily-bf4b61d3.ly">
<img align="middle"
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</p>
</blockquote>
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<p>
<a name="Modifying-context-plug_002dins"></a>
Next: <a rel="next" accesskey="n" href="Changing-context-default-settings.html#Changing-context-default-settings">Changing context default settings</a>,
Previous: <a rel="previous" accesskey="p" href="Creating-contexts.html#Creating-contexts">Creating contexts</a>,
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