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<div class="refentry" title="mode">
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<h2>
<span class="refentrytitle">mode</span>
</h2>
<p>mode —
A filter that simulates a mass-spring-damper system
</p>
</div>
<div class="refsect1" title="Description">
<a id="idp32002664"></a>
<h2>Description</h2>
<p>
Filters the incoming signal with the specified resonance frequency and
quality factor. It can also be seen as a signal generator for high quality
factor, with an impulse for the excitation. You can combine several modes
to built complex instruments such as bells or guitar tables.
</p>
</div>
<div class="refsect1" title="Syntax">
<a id="idp32003576"></a>
<h2>Syntax</h2>
<pre class="synopsis">aout <span class="command"><strong>mode</strong></span> ain, kfreq, kQ [, iskip]</pre>
</div>
<div class="refsect1" title="Initialization">
<a id="idp32050520"></a>
<h2>Initialization</h2>
<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="idp32051432"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>aout</em></span> -- filtered signal
</p>
<p>
<span class="emphasis"><em>ain</em></span> -- signal to filter
</p>
<p>
<span class="emphasis"><em>kfreq</em></span> -- resonant frequency of the filter
</p>
<div class="warning" title="Warning" style="margin-left: 0.5in; margin-right: 0.5in;">
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<th align="left">Warning</th>
</tr>
<tr>
<td align="left" valign="top">
<p>
This filter becomes unstable if <span class="emphasis"><em>sr</em></span>/<span class="emphasis"><em>kfreq</em></span> <
pi (e.g <span class="emphasis"><em>kfreq</em></span> > 14037 Hz @ 44 kHz)
</p>
</td>
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</div>
<p>
</p>
<p>
<span class="emphasis"><em>kQ</em></span> -- quality factor of the filter
</p>
<p>The resonance time is roughly proportionnal to <span class="emphasis"><em>kQ</em></span>/<span class="emphasis"><em>kfreq</em></span>.</p>
<p>
See <a class="link" href="MiscModalFreq.html" title="Appendix E. Modal Frequency Ratios"><em class="citetitle">Modal Frequency Ratios</em></a> for frequency ratios of real intruments which can be used to determine the values of <span class="emphasis"><em>kfreq</em></span>.
</p>
</div>
<div class="refsect1" title="Examples">
<a id="idp32056656"></a>
<h2>Examples</h2>
<p>
Here is an example of the mode opcode. It uses the file <a class="ulink" href="examples/mode.csd" target="_top"><em class="citetitle">mode.csd</em></a>.
</p>
<div class="example">
<a id="idp32057600"></a>
<p class="title">
<strong>Example 487. Example of the mode opcode.</strong>
</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> 2
<span class="oblock">instr</span> 1<span class="comment">; 2 modes excitator</span>
idur <span class="opc">init</span> p3
ifreq11 <span class="opc">init</span> p4
ifreq12 <span class="opc">init</span> p5
iQ11 <span class="opc">init</span> p6
iQ12 <span class="opc">init</span> p7
iamp <span class="opc">init</span> <span class="opc">ampdb</span>(p8)
ifreq21 <span class="opc">init</span> p9
ifreq22 <span class="opc">init</span> p10
iQ21 <span class="opc">init</span> p11
iQ22 <span class="opc">init</span> p12
<span class="comment">; to simulate the shock between the excitator and the resonator</span>
ashock <span class="opc">mpulse</span> 3,0
aexc1 <span class="opc">mode</span> ashock,ifreq11,iQ11
aexc1 <span class="op">=</span> aexc1<span class="op">*</span>iamp
aexc2 <span class="opc">mode</span> ashock,ifreq12,iQ12
aexc2 <span class="op">=</span> aexc2<span class="op">*</span>iamp
aexc <span class="op">=</span> (aexc1<span class="op">+</span>aexc2)<span class="op">/</span>2
<span class="comment">;"Contact" condition : when aexc reaches 0, the excitator looses </span>
<span class="comment">;contact with the resonator, and stops "pushing it"</span>
aexc <span class="opc">limit</span> aexc,0,3<span class="op">*</span>iamp
<span class="comment">; 2modes resonator</span>
ares1 <span class="opc">mode</span> aexc,ifreq21,iQ21
ares2 <span class="opc">mode</span> aexc,ifreq22,iQ22
ares <span class="op">=</span> (ares1<span class="op">+</span>ares2)<span class="op">/</span>2
<span class="opc">display</span> aexc<span class="op">+</span>ares,p3
<span class="opc">outs</span> aexc<span class="op">+</span>ares,aexc<span class="op">+</span>ares
<span class="oblock">endin</span>
<span class="csdtag"></CsInstruments></span>
<span class="csdtag"><CsScore></span>
<span class="comment">;wooden excitator against glass resonator</span>
<span class="stamnt">i</span>1 0 8 1000 3000 12 8 70 440 888 500 420
<span class="comment">;felt against glass</span>
<span class="stamnt">i</span>1 4 8 80 188 8 3 70 440 888 500 420
<span class="comment">;wood against wood</span>
<span class="stamnt">i</span>1 8 8 1000 3000 12 8 70 440 630 60 53
<span class="comment">;felt against wood</span>
<span class="stamnt">i</span>1 12 8 80 180 8 3 70 440 630 60 53
<span class="stamnt">i</span>1 16 8 1000 3000 12 8 70 440 888 2000 1630
<span class="stamnt">i</span>1 23 8 80 180 8 3 70 440 888 2000 1630
<span class="comment">;With a metallic excitator</span>
<span class="stamnt">i</span>1 33 8 1000 1800 1000 720 70 440 882 500 500
<span class="stamnt">i</span>1 37 8 1000 1800 1000 850 70 440 630 60 53
<span class="stamnt">i</span>1 42 8 1000 1800 2000 1720 70 440 442 500 500
<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="idp32059864"></a>
<h2>Credits</h2>
<p>Original UDO and documentation/example by François Blanc</p>
<p>Opcode translation to C-code by Steven Yi</p>
<p>New in version 5.04</p>
</div>
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