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<div class="refentry" title="moogvcf2">
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<h2>
<span class="refentrytitle">moogvcf2</span>
</h2>
<p>moogvcf2 —
A digital emulation of the Moog diode ladder filter configuration.
</p>
</div>
<div class="refsect1" title="Description">
<a id="id3039352"></a>
<h2>Description</h2>
<p>
A digital emulation of the Moog diode ladder filter configuration.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="id3039364"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>moogvcf2</strong></span> asig, xfco, xres [,iscale, iskip]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="id3039382"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>iscale</em></span> (optional, default=0dBfs) -- internal
scaling factor, as the operation of the code requires the signal
to be in the range +/-1. Input is first divided by
<span class="emphasis"><em>iscale</em></span>, then output is mutliplied by
<span class="emphasis"><em>iscale</em></span>.
</p>
<p>
<span class="emphasis"><em>iskip</em></span> (optional, default=0) -- if non zero
skip the initialisation of the filter.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="id3040311"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>asig</em></span> -- input signal
</p>
<p>
<span class="emphasis"><em>xfco</em></span> -- filter cut-off frequency in
Hz. which may be i-,k-, or a-rate.
</p>
<p>
<span class="emphasis"><em>xres</em></span> -- amount of
resonance. Self-oscillation occurs when <span class="emphasis"><em>xres</em></span>
is approximately one. May be a-rate, i-rate, or k-rate.
</p>
<p>
<span class="emphasis"><em>moogvcf2</em></span> is a digital emulation of the Moog
diode ladder filter configuration. This emulation is based loosely
on the paper <span class="quote">“<span class="quote">Analyzing the Moog VCF with Considerations for
Digital Implementation</span>”</span> by Stilson and Smith (CCRMA). This
version was originally coded in Csound by Josep Comajuncosas. Some
modifications and conversion to C were done by Hans Mikelson and then
adjusted.
</p>
<p>
<span class="emphasis"><em>moogvcf2</em></span> is identical to <a class="link" href="moogvcf.html" title="moogvcf"><em class="citetitle">moogvcf</em></a>, except that the
<span class="emphasis"><em>iscale</em></span> parameter defaults to <a class="link" href="Zerodbfs.html" title="0dbfs"><em class="citetitle">0dbfs</em></a> instead of 0, guaranteeing that amplitude will usually be OK.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="id3040391"></a>
<h2>Examples</h2>
<p>
Here is an example of the moogvcf2 opcode. It uses the file <a class="ulink" href="examples/moogvcf2.csd" target="_top"><em class="citetitle">moogvcf2.csd</em></a>.
</p>
<div class="example">
<a id="id3040407"></a>
<p class="title">
<b>Example 380. Example of the moogvcf2 opcode.</b>
</p>
<div class="example-contents">
<p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
<pre class="programlisting">
<span class="csdtag"><CsoundSynthesizer></span>
<span class="csdtag"><CsOptions></span>
<span class="comment">; Select audio/midi flags here according to platform</span>
<span class="comment">; Audio out Audio in No messages</span>
-odac -iadc -d <span class="comment">;;;RT audio I/O</span>
<span class="comment">; For Non-realtime ouput leave only the line below:</span>
<span class="comment">; -o moogvcf.wav -W ;;; for file output any platform</span>
<span class="csdtag"></CsOptions></span>
<span class="csdtag"><CsInstruments></span>
<span class="comment">; Initialize the global variables.</span>
<span class="ohdr">sr</span> <span class="op">=</span> 44100
<span class="ohdr">kr</span> <span class="op">=</span> 4410
<span class="ohdr">ksmps</span> <span class="op">=</span> 10
<span class="ohdr">nchnls</span> <span class="op">=</span> 1
<span class="comment">; Instrument #1.</span>
<span class="oblock">instr</span> 1
<span class="comment">; Use a nice sawtooth waveform.</span>
asig <span class="opc">vco</span> 32000, 220, 1
<span class="comment">; Vary the filter-cutoff frequency from .2 to 2 KHz.</span>
kfco <span class="opc">line</span> 200, p3, 2000
<span class="comment">; Set the resonance amount to one.</span>
krez <span class="opc">init</span> 1
a1 <span class="opc">moogvcf2</span> asig, kfco, krez
<span class="opc">out</span> a1
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">; Table #1, a sine wave for the vco opcode.</span>
<span class="stamnt">f</span> 1 0 16384 10 1
<span class="comment">; Play Instrument #1 for three seconds.</span>
<span class="stamnt">i</span> 1 0 3
<span class="stamnt">e</span>
<span class="csdtag"></CsScore></span>
<span class="csdtag"></CsoundSynthesizer></span>
</pre>
</div>
</div>
<p><br class="example-break" />
</p>
</div>
<div class="refsect1" title="See Also">
<a id="id3040445"></a>
<h2>See Also</h2>
<p>
<a class="link" href="moogvcf.html" title="moogvcf"><em class="citetitle">moogvcf</em></a>,
<a class="link" href="biquad.html" title="biquad"><em class="citetitle">biquad</em></a>,
<a class="link" href="rezzy.html" title="rezzy"><em class="citetitle">rezzy</em></a>
</p>
</div>
<div class="refsect1" title="Credits">
<a id="id3040478"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Hans Mikelson and John ffitch</td>
</tr>
<tr>
<td>October 1998/ July 2006</td>
</tr>
</table>
<p>
</p>
<p>Example written by Kevin Conder.</p>
<p>New in Csound version 5.03</p>
</div>
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