<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>foscil</title>
<link rel="stylesheet" href="csound.css" type="text/css" />
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2" />
<link rel="home" href="index.html" title="The Canonical Csound Reference Manual" />
<link rel="up" href="OpcodesTop.html" title="Orchestra Opcodes and Operators" />
<link rel="prev" href="follow2.html" title="follow2" />
<link rel="next" href="foscili.html" title="foscili" />
</head>
<body>
<div class="navheader">
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">foscil</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="follow2.html">Prev</a> </td>
<th width="60%" align="center">Orchestra Opcodes and Operators</th>
<td width="20%" align="right"> <a accesskey="n" href="foscili.html">Next</a></td>
</tr>
</table>
<hr />
</div>
<div class="refentry" title="foscil">
<a id="foscil"></a>
<div class="titlepage"></div>
<a id="Indexfoscil" class="indexterm"></a>
<div class="refnamediv">
<h2>
<span class="refentrytitle">foscil</span>
</h2>
<p>foscil —
A basic frequency modulated oscillator.
</p>
</div>
<div class="refsect1" title="Description">
<a id="id2913958"></a>
<h2>Description</h2>
<p>
A basic frequency modulated oscillator.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="id2913970"></a>
<h2>Syntax</h2>
<pre class="synopsis">ares <span class="command"><strong>foscil</strong></span> xamp, kcps, xcar, xmod, kndx, ifn [, iphs]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="id2914896"></a>
<h2>Initialization</h2>
<p>
<span class="emphasis"><em>ifn</em></span> -- function table number. Requires a wrap-around guard point.
</p>
<p>
<span class="emphasis"><em>iphs</em></span> (optional, default=0) -- initial phase of waveform in table <span class="emphasis"><em>ifn</em></span>, expressed as a fraction of a cycle (0 to 1). A negative value will cause phase initialization to be skipped. The default value is 0.
</p>
</div>
<div class="refsect1" title="Performance">
<a id="id2914928"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>xamp</em></span> -- the amplitude of the output signal.
</p>
<p>
<span class="emphasis"><em>kcps</em></span> -- a common denominator, in cycles per second, for the carrier and modulating frequencies.
</p>
<p>
<span class="emphasis"><em>xcar</em></span> -- a factor that, when multiplied by the <span class="emphasis"><em>kcps</em></span> parameter, gives the carrier frequency.
</p>
<p>
<span class="emphasis"><em>xmod</em></span> -- a factor that, when multiplied by the <span class="emphasis"><em>kcps</em></span> parameter, gives the modulating frequency.
</p>
<p>
<span class="emphasis"><em>kndx</em></span> -- the modulation index.
</p>
<p>
<span class="emphasis"><em>foscil</em></span> is a composite unit that effectively
banks two <span class="emphasis"><em>oscil</em></span> opcodes in the familiar
Chowning FM setup, wherein the audio-rate output of one
generator is used to modulate the frequency input of another
(the <span class="quote">“<span class="quote">carrier</span>”</span>). Effective carrier frequency =
<span class="emphasis"><em>kcps</em></span> * <span class="emphasis"><em>xcar</em></span>, and
modulating frequency = <span class="emphasis"><em>kcps</em></span> *
<span class="emphasis"><em>xmod</em></span>. For integral values of
<span class="emphasis"><em>xcar</em></span> and <span class="emphasis"><em>xmod</em></span>, the
perceived fundamental will be the minimum positive value of
<span class="emphasis"><em>kcps</em></span> * (<span class="emphasis"><em>xcar</em></span> - <span class="emphasis"><em>n</em></span> *
<span class="emphasis"><em>xmod</em></span>), <span class="emphasis"><em>n</em></span> = 0,1,2,... The input
<span class="emphasis"><em>kndx</em></span> is the index of modulation (usually
time-varying and ranging 0 to 4 or so) which determines the
spread of acoustic energy over the partial positions given by <span class="emphasis"><em>n</em></span>
= 0,1,2,.., etc. <span class="emphasis"><em>ifn</em></span> should point to a
stored sine wave. Previous to version 3.50,
<span class="emphasis"><em>xcar</em></span> and <span class="emphasis"><em>xmod</em></span> could be
k-rate only.
</p>
<p>
The actual formula used for this implementation of FM synthesis
is
<span class="emphasis"><em>xamp</em></span> * cos(2π * <span class="emphasis"><em>t</em></span> * <span class="emphasis"><em>kcps</em></span> *
<span class="emphasis"><em>xcar</em></span> +
<span class="emphasis"><em>kndx</em></span> * sin(2π * <span class="emphasis"><em>t </em></span>* <span class="emphasis"><em>kcps</em></span> *
<span class="emphasis"><em>xmod</em></span>) - π),
assuming that the table is a sine wave.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="id2915115"></a>
<h2>Examples</h2>
<p>
Here is an example of the foscil opcode. It uses the file <a class="ulink" href="examples/foscil.csd" target="_top"><em class="citetitle">foscil.csd</em></a>.
</p>
<div class="example">
<a id="id2915132"></a>
<p class="title">
<b>Example 260. Example of the foscil 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 foscil.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 - a basic FM waveform.</span>
<span class="oblock">instr</span> 1
kamp <span class="op">=</span> 10000
kcps <span class="op">=</span> 440
kcar <span class="op">=</span> 600
kmod <span class="op">=</span> 210
kndx <span class="op">=</span> 2
ifn <span class="op">=</span> 1
a1 <span class="opc">foscil</span> kamp, kcps, kcar, kmod, kndx, ifn
<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.</span>
<span class="stamnt">f</span> 1 0 16384 10 1
<span class="comment">; Play Instrument #1 for 2 seconds.</span>
<span class="stamnt">i</span> 1 0 2
<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="Credits">
<a id="id2915170"></a>
<h2>Credits</h2>
<p>Example written by Kevin Conder.</p>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="follow2.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="OpcodesTop.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="foscili.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">follow2 </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> foscili</td>
</tr>
</table>
</div>
</body>
</html>
