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<p>
<a name="Collision-resolution"></a>
Next: <a rel="next" accesskey="n" href="Automatic-part-combining.html#Automatic-part-combining">Automatic part combining</a>,
Previous: <a rel="previous" accesskey="p" href="Voice-styles.html#Voice-styles">Voice styles</a>,
Up: <a rel="up" accesskey="u" href="Multiple-voices.html#Multiple-voices">Multiple voices</a>
<hr>
</div>
<h5 class="unnumberedsubsubsec">Collision resolution</h5>
<p><a name="index-merging-notes-1262"></a><a name="index-note-collisions-1263"></a><a name="index-collisions-1264"></a><a name="index-g_t_005cshiftOn-1265"></a><a name="index-g_t_005cshiftOn-1266"></a>
<a name="index-g_t_005cshiftOnn-1267"></a><a name="index-g_t_005cshiftOnn-1268"></a>
<a name="index-g_t_005cshiftOnnn-1269"></a><a name="index-g_t_005cshiftOnnn-1270"></a>
<a name="index-g_t_005cshiftOff-1271"></a><a name="index-g_t_005cshiftOff-1272"></a>
<a name="index-shift-rest_002c-automatic-1273"></a>
Note heads with equal durations are automatically merged, while
note heads with unequal durations are not merged. Rests opposite
a stem are shifted vertically.
<blockquote>
<pre class="verbatim">
<<
{
c8 d e d c d c4
g'2 fis
} \\ {
c2 c8. b16 c4
e,2 r
} \\ {
\oneVoice
s1
e8 a b c d2
}
>>
</pre>
<p>
<a href="../b8/lily-c089b276.ly">
<img align="middle"
border="0" src="../b8/lily-c089b276.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p>Note heads with different note heads may be merged, with the
exception of half-note heads and quarter-note heads:
<blockquote>
<pre class="verbatim">
<<
{
\mergeDifferentlyHeadedOn
c8 d e d c d c4
g'2 fis
} \\ {
c2 c8. b16 c4
e,2 r
} \\ {
\oneVoice
s1
e8 a b c d2
}
>>
</pre>
<p>
<a href="../cf/lily-4daf1523.ly">
<img align="middle"
border="0" src="../cf/lily-4daf1523.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p>Note heads with different dots may be merged:
<blockquote>
<pre class="verbatim">
<<
{
\mergeDifferentlyHeadedOn
\mergeDifferentlyDottedOn
c8 d e d c d c4
g'2 fis
} \\ {
c2 c8. b16 c4
e,2 r
} \\ {
\oneVoice
s1
e8 a b c d2
}
>>
</pre>
<p>
<a href="../a0/lily-0d70efbb.ly">
<img align="middle"
border="0" src="../a0/lily-0d70efbb.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p><a name="index-shift-note-1274"></a>
The collision on the second measure happens because
<code>merge-differently-headed</code> cannot successfully complete the
merge when three or more notes line up in the same column – in
fact, you will obtain a warning for this reason. To allow the
merge to work properly, apply a <code>\shift</code> to the note that
should not be merged. Here, <code>\shiftOn</code> is applied to move
the top <code>g</code> out of the column, and
<code>merge-differently-headed</code> works properly.
<blockquote>
<pre class="verbatim">
<<
{
\mergeDifferentlyHeadedOn
\mergeDifferentlyDottedOn
c8 d e d c d c4
\shiftOn
g'2 fis
} \\ {
c2 c8. b16 c4
e,2 r
} \\ {
\oneVoice
s1
e8 a b c d2
}
>>
</pre>
<p>
<a href="../6a/lily-6090b616.ly">
<img align="middle"
border="0" src="../6a/lily-6090b616.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p>The <code>\shiftOn</code>, <code>\shiftOnn</code>, and <code>\shiftOnnn</code>
commands specify the degree to which chords of the current voice
should be shifted. The outer voices (normally: voices one and
two) have <code>\shiftOff</code>, while the inner voices (three and
four) have <code>\shiftOn</code>. <code>\shiftOnn</code> and
<code>\shiftOnnn</code> define further shift levels.
<p>Notes are only merged if they have opposing stem directions (i.e., in
<code>Voice</code> 1 and 2).
<p><a name="index-multiple-voices-1275"></a><a name="index-polyphonic-music-1276"></a><a name="index-shifting-voices-1277"></a>
<h5 class="subsubheading">Predefined commands</h5>
<p><a name="index-g_t_005cmergeDifferentlyDottedOn-1278"></a><a name="index-g_t_005cmergeDifferentlyDottedOn-1279"></a>
<code>\mergeDifferentlyDottedOn</code>,
<a name="index-g_t_005cmergeDifferentlyDottedOff-1280"></a><a name="index-g_t_005cmergeDifferentlyDottedOff-1281"></a>
<code>\mergeDifferentlyDottedOff</code>,
<a name="index-g_t_005cmergeDifferentlyHeadedOn-1282"></a><a name="index-g_t_005cmergeDifferentlyHeadedOn-1283"></a>
<code>\mergeDifferentlyHeadedOn</code>,
<a name="index-g_t_005cmergeDifferentlyHeadedOff-1284"></a><a name="index-g_t_005cmergeDifferentlyHeadedOff-1285"></a>
<code>\mergeDifferentlyHeadedOff</code>.
<p><a name="index-g_t_005cshiftOn-1286"></a><a name="index-g_t_005cshiftOn-1287"></a>
<code>\shiftOn</code>,
<a name="index-g_t_005cshiftOnn-1288"></a><a name="index-g_t_005cshiftOnn-1289"></a>
<code>\shiftOnn</code>,
<a name="index-g_t_005cshiftOnnn-1290"></a><a name="index-g_t_005cshiftOnnn-1291"></a>
<code>\shiftOnnn</code>,
<a name="index-g_t_005cshiftOff-1292"></a><a name="index-g_t_005cshiftOff-1293"></a>
<code>\shiftOff</code>.
<p class="noindent">
<h5 class="subsubheading">Selected Snippets</h5>
<p><em>Additional voices to avoid collisions</em>
<p>In some instances of complex polyphonic music, additional voices are
necessary to prevent collisions between notes. If more than four
parallel voices are needed, additional voices can be added by defining
a variable using the Scheme function <code>context-spec-music</code>.
<blockquote>
<pre class="verbatim">
voiceFive = #(context-spec-music (make-voice-props-set 4) 'Voice)
\relative c'' {
\time 3/4 \key d \minor \partial 2
<<
{ \voiceOne
a4. a8
e'4 e4. e8
f4 d4. c8
} \\ {
\voiceThree
f,2
bes4 a2
a4 s2
} \\ {
\voiceFive
s2
g4 g2
f4 f2
} \\ {
\voiceTwo
d2
d4 cis2
d4 bes2
}
>>
}
</pre>
<p>
<a href="../1c/lily-1a8c4f9e.ly">
<img align="middle"
border="0" src="../1c/lily-1a8c4f9e.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p><em>Forcing horizontal shift of notes</em>
<p>When the typesetting engine cannot cope, the <code>force-hshift</code>
property of the <code>NoteColumn</code> object can be used to override
typesetting decisions. The measure units used here are staff spaces.
<blockquote>
<pre class="verbatim">
\relative c' <<
{
<d g>2 <d g>
}
\\
{ <b f'>2
\once \override NoteColumn #'force-hshift = #1.7
<b f'>2
}
>>
</pre>
<p>
<a href="../ca/lily-9af05dc8.ly">
<img align="middle"
border="0" src="../ca/lily-9af05dc8.png" alt="[image of music]">
</a>
</p>
</blockquote>
<p class="noindent">
<h5 class="subsubheading">See also</h5>
<p class="indent">
<p>Music Glossary:
<a name="index-polyphony-1294"></a><a href="../music-glossary/polyphony.html#polyphony">polyphony</a>.
<p>Learning Manual:
<a name="index-Multiple-notes-at-once-1295"></a><a href="../lilypond-learning/Multiple-notes-at-once.html#Multiple-notes-at-once">Multiple notes at once</a>,
<a name="index-Voices-contain-music-1296"></a><a href="../lilypond-learning/Voices-contain-music.html#Voices-contain-music">Voices contain music</a>,
<a name="index-Collisions-of-objects-1297"></a><a href="../lilypond-learning/Collisions-of-objects.html#Collisions-of-objects">Collisions of objects</a>.
<p>Snippets:
<a href="../../../input/lsr/lilypond-snippets/Simultaneous-notes.html#Simultaneous-notes">Simultaneous notes</a>.
<p>Internals Reference:
<a name="index-NoteColumn-1298"></a><a href="../lilypond-internals/NoteColumn.html#NoteColumn">NoteColumn</a>,
<a name="index-NoteCollision-1299"></a><a href="../lilypond-internals/NoteCollision.html#NoteCollision">NoteCollision</a>,
<a name="index-RestCollision-1300"></a><a href="../lilypond-internals/RestCollision.html#RestCollision">RestCollision</a>.
<p class="noindent">
<h5 class="subsubheading">Known issues and warnings</h5>
<p>When using <code>merge-differently-headed</code> with an upstem eighth
or a shorter note, and a downstem half note, the eighth note stem
gets a slightly wrong offset because of the different width of the
half note head symbol.
<!-- investigate! Sometimes it works, sometimes not. -FV -->
<p>The requirements for successfully merging different note heads that
are at the same time differently dotted are not clear.
<p>There is no support for chords where the same note occurs with
different accidentals in the same chord. In this case, it is
recommended to use enharmonic transcription, or to use special
cluster notation (see <a href="Clusters.html#Clusters">Clusters</a>).
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Previous: <a rel="previous" accesskey="p" href="Voice-styles.html#Voice-styles">Voice styles</a>,
Up: <a rel="up" accesskey="u" href="Multiple-voices.html#Multiple-voices">Multiple voices</a>
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