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<div class="refentry" title="crossfm">
<a id="crossfm"></a>
<div class="titlepage"></div>
<a id="Indexcrossfm" class="indexterm"></a>
<div class="refnamediv">
<h2>
<span class="refentrytitle">crossfm</span>
</h2>
<p>crossfm —
Two mutually frequency and/or phase modulated oscillators.
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp17227616"></a>
<h2>Description</h2>
<p>
Two oscillators, mutually frequency and/or phase modulated by each other.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp17228304"></a>
<h2>Syntax</h2>
<pre class="synopsis">a1, a2 <span class="command"><strong>crossfm</strong></span> xfrq1, xfrq2, xndx1, xndx2, kcps, ifn1, ifn2 [, iphs1] [, iphs2]</pre>
<pre class="synopsis">a1, a2 <span class="command"><strong>crossfmi</strong></span> xfrq1, xfrq2, xndx1, xndx2, kcps, ifn1, ifn2 [, iphs1] [, iphs2]</pre>
<pre class="synopsis">a1, a2 <span class="command"><strong>crosspm</strong></span> xfrq1, xfrq2, xndx1, xndx2, kcps, ifn1, ifn2 [, iphs1] [, iphs2]</pre>
<pre class="synopsis">a1, a2 <span class="command"><strong>crosspmi</strong></span> xfrq1, xfrq2, xndx1, xndx2, kcps, ifn1, ifn2 [, iphs1] [, iphs2]</pre>
<pre class="synopsis">a1, a2 <span class="command"><strong>crossfmpm</strong></span> xfrq1, xfrq2, xndx1, xndx2, kcps, ifn1, ifn2 [, iphs1] [, iphs2]</pre>
<pre class="synopsis">a1, a2 <span class="command"><strong>crossfmpmi</strong></span> xfrq1, xfrq2, xndx1, xndx2, kcps, ifn1, ifn2 [, iphs1] [, iphs2]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp17242744"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>ifn1</em></span> -- function table number for oscillator #1.
Requires a wrap-around guard point.
</p>
<p>
<span class="emphasis"><em>ifn2</em></span> -- function table number for oscillator #2.
Requires a wrap-around guard point.
</p>
<p>
<span class="emphasis"><em>iphs1</em></span> (optional, default=0) -- initial phase of waveform
in table <span class="emphasis"><em>ifn1</em></span>, expressed as a fraction of a cycle (0 to 1).
A negative value will cause phase initialization to be skipped.
</p>
<p>
<span class="emphasis"><em>iphs2</em></span> (optional, default=0) -- initial phase of waveform
in table <span class="emphasis"><em>ifn2</em></span>, expressed as a fraction of a cycle (0 to 1).
A negative value will cause phase initialization to be skipped.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="idp17278960"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>xfrq1</em></span> -- a factor that, when multipled by the
<span class="emphasis"><em>kcps</em></span> parameter, gives the frequency of oscillator #1.
</p>
<p>
<span class="emphasis"><em>xfrq2</em></span> -- a factor that, when multipled by the
<span class="emphasis"><em>kcps</em></span> parameter, gives the frequency of oscillator #2.
</p>
<p>
<span class="emphasis"><em>xndx1</em></span> -- the index of the modulation of oscillator #2
by oscillator #1.
</p>
<p>
<span class="emphasis"><em>xndx2</em></span> -- the index of the modulation of oscillator #1
by oscillator #2.
</p>
<p>
<span class="emphasis"><em>kcps</em></span> -- a common denominator, in cycles per second,
for both oscillators frequencies.
</p>
<p>
<span class="emphasis"><em>crossfm</em></span> implements a crossed frequency modulation
algorithm. The audio-rate output of oscillator #1 is used to modulate the
frequency input of oscillator #2 while the audio-rate output of oscillator #2
is used to modulate the frequency input of oscillator #1. This double feedback
structure produces a rich set of sounds with some chaotic behaviour.
<span class="emphasis"><em>crossfmi</em></span> behaves like <span class="emphasis"><em>crossfm</em></span>
except that linear interpolation is used for table lookup.
</p>
<p>
<span class="emphasis"><em>crosspm</em></span> and <span class="emphasis"><em>crosspmi</em></span> implement
cross phase modulation between two oscillators.
</p>
<p>
<span class="emphasis"><em>crossfmpm</em></span> and <span class="emphasis"><em>crossfmpmi</em></span>
implement cross frequency/phase modulation between two oscillators.
Oscillator #1 is frequency-modulated by oscillator #2 while oscillator #2
is phase-modulated by oscillator #1.
</p>
<p>
You can read my <a class="ulink" href="http://www.csounds.com/journal/issue12/crossfm.html" target="_top"><em class="citetitle">paper</em></a>
in the Csound Journal for more information.
</p>
<div class="warning" title="Warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Warning: Warning">
<tr>
<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Warning]" src="images/warning.png" />
</td>
<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>
Those opcodes may produce very rich spectra, especially with high
modulation indexes, and in some cases foldover aliases may occur if the
sampling rate is not high enough. Moreover the audio output may vary in
function of the sampling rate, due to the non-linearity of the algorithm.
In Csound, two other opcodes have this characteristic:
<span class="emphasis"><em>planet</em></span> and <span class="emphasis"><em>chuap</em></span>.
</p>
</td>
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</div>
<div class="refsect1" title="Examples">
<a id="idp17287280"></a>
<h2>Examples</h2>
<p>
Here is an example of the crossfm opcode. It uses the file
<a class="ulink" href="examples/crossfm.csd" target="_top"><em class="citetitle">crossfm.csd</em></a>.
</p>
<div class="example">
<a id="idp17288264"></a>
<p class="title">
<strong>Example 145. Example of the crossfm opcode.</strong>
</p>
<div class="example-contents">
<pre class="programlisting">
<span class="csdtag"><CsoundSynthesizer></span>
<span class="csdtag"><CsOptions></span>
-d -o dac
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="ohdr">sr</span> <span class="op">=</span> 96000
<span class="ohdr">ksmps</span> <span class="op">=</span> 10
<span class="ohdr">nchnls</span> <span class="op">=</span> 2
<span class="ohdr">0dbfs</span> <span class="op">=</span> 1
<span class="opc">FLpanel</span> "crossfmForm", 600, 400, 0, 0
gkfrq1, ihfrq1 <span class="opc">FLcount</span> "Freq #1", 0, 20000, 0.001, 1, 1, 200, 30, 20, 50, <span class="op">-</span>1
gkfrq2, ihfrq2 <span class="opc">FLcount</span> "Freq #2", 0, 20000, 0.001, 1, 1, 200, 30, 20, 130, <span class="op">-</span>1
gkndx1, gkndx2, ihndx1, ihndx2 <span class="opc">FLjoy</span> "Indexes", 0, 10, 0, 10, 0, 0, <span class="op">-</span>1, <span class="op">-</span>1, 200, 200, 300, 50
<span class="opc">FLsetVal_i</span> 164.5, ihfrq1
<span class="opc">FLsetVal_i</span> 263.712, ihfrq2
<span class="opc">FLsetVal_i</span> 1.5, ihndx1
<span class="opc">FLsetVal_i</span> 3, ihndx2
<span class="opc">FLpanelEnd</span>
<span class="opc">FLrun</span>
<span class="opc">maxalloc</span> 1, 2
<span class="oblock">instr</span> 1
kamp <span class="opc">linen</span> 0.5, 0.01, p3, 0.5
a1,a2 <span class="opc">crossfm</span> gkfrq1, gkfrq2, gkndx1, gkndx2, 1, 1, 1
<span class="opc">outs</span> a1<span class="op">*</span>kamp, a2<span class="op">*</span>kamp
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="stamnt">f</span>1 0 16384 10 1 0
<span class="stamnt">i</span>1 0 60
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
</p>
<p>
In this example, an FLTK GUI is used to control in real-time the oscillators
frequency with two <span class="emphasis"><em>Flcount</em></span> widgets and the cross
modulation indexes with one <span class="emphasis"><em>FLjoy</em></span> widget. It uses a
sampling rate of 96000Hz.
</p>
</div>
<div class="refsect1" title="See Also">
<a id="idp17290120"></a>
<h2>See Also</h2>
<p> More information on this opcode: <a class="ulink" href="http://www.csounds.com/journal/issue12/crossfm.html" target="_top"><em class="citetitle">http://www.csounds.com/journal/issue12/crossfm.html</em></a> , written by François Pinot </p>
</div>
<div class="refsect1" title="Credits">
<a id="idp17291312"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: François Pinot</td>
</tr>
<tr>
<td>2005-2009</td>
</tr>
</table>
<p>
</p>
<p>New in version 5.12</p>
<p>
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