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<a name="Overview-of-music-functions"></a>
Next: <a rel="next" accesskey="n" href="Simple-substitution-functions.html#Simple-substitution-functions">Simple substitution functions</a>,
Up: <a rel="up" accesskey="u" href="Music-functions.html#Music-functions">Music functions</a>
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<h4 class="subsection">6.1.1 Overview of music functions</h4>
<p>Making a function which substitutes a variable into LilyPond
code is easy. The general form of these functions is
<pre class="example">function =
#(define-music-function (parser location <var>var1</var> <var>var2</var>... )
(<var>var1-type?</var> <var>var2-type?</var>...)
#{
<em>...music...</em>
#})
</pre>
<p class="noindent">where
<p><table summary=""><tr align="left"><td valign="top" width="33%"><var>argi</var> </td><td valign="top" width="66%"><var>i</var>th variable
<br></td></tr><tr align="left"><td valign="top" width="33%"><var>argi-type?</var> </td><td valign="top" width="66%">type of variable
<br></td></tr><tr align="left"><td valign="top" width="33%"><var>...music...</var> </td><td valign="top" width="66%">normal LilyPond input, using
variables as <code>#$var1</code>.
<br></td></tr></table>
<p>There following input types may be used as variables
in a music function. This list is not exhaustive; see
other documentation specifically about Scheme for more
variable types.
<p><table summary=""><tr align="left"><th valign="top" width="33%">Input type </th><th valign="top" width="66%"><var>argi-type?</var> notation
<br></th></tr><tr align="left"><td valign="top" width="33%">Integer </td><td valign="top" width="66%"><code>integer?</code>
<br></td></tr><tr align="left"><td valign="top" width="33%">Float (decimal number) </td><td valign="top" width="66%"><code>number?</code>
<br></td></tr><tr align="left"><td valign="top" width="33%">Text string </td><td valign="top" width="66%"><code>string?</code>
<br></td></tr><tr align="left"><td valign="top" width="33%">Markup </td><td valign="top" width="66%"><code>markup?</code>
<br></td></tr><tr align="left"><td valign="top" width="33%">Music expression </td><td valign="top" width="66%"><code>ly:music?</code>
<br></td></tr><tr align="left"><td valign="top" width="33%">A pair of variables </td><td valign="top" width="66%"><code>pair?</code>
<br></td></tr></table>
<p>The <code>parser</code> and <code>location</code> argument are mandatory,
and are used in some advanced situations. The <code>parser</code>
argument is used to access to the value of another LilyPond
variable. The <code>location</code> argument
is used to set the ‘origin’ of the music expression that is built
by the music function, so that in case of a syntax error LilyPond
can tell the user an appropriate place to look in the input file.
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Next: <a rel="next" accesskey="n" href="Simple-substitution-functions.html#Simple-substitution-functions">Simple substitution functions</a>,
Up: <a rel="up" accesskey="u" href="Music-functions.html#Music-functions">Music functions</a>
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