<!-- Converted to DocBook/SGML by Kevin Conder -->
<refentry id="moogvcf">
  <refmeta>
    <refentrytitle>moogvcf</refentrytitle>
  </refmeta>
 
  <refnamediv>
    <refname>moogvcf</refname>
    <refpurpose>
      A digital emulation of the Moog diode ladder filter configuration.
      <indexterm id="IndexMoogvcf"><primary>moogvcf</primary></indexterm>
    </refpurpose>
  </refnamediv>
 
  <refsect1>
    <title>Description</title>
    <para>
      A digital emulation of the Moog diode ladder filter configuration.
    </para>
  </refsect1>
 
  <refsect1>
    <title>Syntax</title>
    <synopsis>ar <command>moogvcf</command> asig, xfco, xres [, iscale]</synopsis>
  </refsect1>
 
  <refsect1>
    <title>Initialization</title>
    <para>
      <emphasis>iscale</emphasis> (optional, default=1) -- internal scaling factor. Use if <emphasis>asig</emphasis> is not in the range +/-1. Input is first divided by <emphasis>iscale</emphasis>, then output is mutliplied <emphasis>iscale</emphasis>. Default value is 1. (New in Csound version 3.50)
    </para>
  </refsect1>
 
  <refsect1>
    <title>Performance</title>
    <para>
      <emphasis>asig</emphasis> -- input signal
    </para>

    <para>
      <emphasis>xfco</emphasis> -- filter cut-off frequency in Hz. As of version 3.50, may i-,k-, or a-rate.
    </para>

    <para>
      <emphasis>xres</emphasis> -- amount of resonance. Self-oscillation occurs when <emphasis>xres</emphasis> is approximately one. As of version 3.50, may a-rate, i-rate, or k-rate.
    </para>

    <para>
      <emphasis>moogvcf</emphasis> is a digital emulation of the Moog diode ladder filter configuration. This emulation is based loosely on the paper <quote>Analyzing the Moog VCF with Considerations for Digital Implemnetation</quote> by Stilson and Smith (CCRMA). This version was originally coded in Csound by Josep Comajuncosas. Some modifications and conversion to C were done by &namehans;
    </para>

    <para>
      <emphasis>Note</emphasis>: This filter requires that the input signal be normalized to one.
    </para>
  </refsect1>

  <refsect1>
    <title>Examples</title>
    <para>
      Here is an example of the moogvcf opcode. It uses the files <ulink url="examples/moogvcf.orc"><citetitle>moogvcf.orc</citetitle></ulink> and <ulink url="examples/moogvcf.sco"><citetitle>moogvcf.sco</citetitle></ulink>.

      <example>
        <title>Example of the moogvcf opcode.</title>

        <programlisting>
<inlinemediaobject>
            <imageobject>
              <imagedata fileref="examples/moogvcf.orc" format="linespecific">
            </imageobject>
          </inlinemediaobject>
        </programlisting>

        <programlisting>
<inlinemediaobject>
            <imageobject>
              <imagedata fileref="examples/moogvcf.sco" format="linespecific">
            </imageobject>
          </inlinemediaobject>
        </programlisting>
      </example>
    </para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <link linkend="biquad"><citetitle>biquad</citetitle></link>,
      <link linkend="rezzy"><citetitle>rezzy</citetitle></link>
    </para>
  </refsect1>
 
  <refsect1>
    <title>Credits</title>
    <para>
      <simplelist>
        <member>Author: &namehans;</member>
        <member>October 1998</member>
      </simplelist>
    </para>
    <para>Example written by &namekevin;.</para>

    <para>New in Csound version 3.49</para>
  </refsect1>
</refentry>
