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<section id="exponential-ramp-py-exponential-portamento-with-rising-and-falling-times">
<h1>03-exponential-ramp.py - Exponential portamento with rising and falling times.<a class="headerlink" href="#exponential-ramp-py-exponential-portamento-with-rising-and-falling-times" title="Permalink to this heading">¶</a></h1>
<p>The Port object is designed to lowpass filter an audio signal with
different coefficients for rising and falling signals. A lowpass
filter is a good and efficient way of creating an exponential ramp
from a signal containing abrupt changes. The rising and falling
coefficients are controlled in seconds.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <a class="sphinx-codeautolink-a" href="../../api/alphabetical.html#module-pyo" title="pyo"><span class="nn">pyo</span></a> <span class="kn">import</span> <span class="o">*</span>
<span class="n">s</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/server.html#pyo.Server" title="pyo.lib.server.Server"><span class="n">Server</span></a><span class="p">()</span><span class="o">.</span><span class="n">boot</span><span class="p">()</span>
<span class="c1"># 2 seconds linear ramp starting at 0.0 and ending at 0.3.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.SigTo" title="pyo.lib.controls.SigTo"><span class="n">amp</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.SigTo" title="pyo.lib.controls.SigTo"><span class="n">SigTo</span></a><span class="p">(</span><span class="n">value</span><span class="o">=</span><span class="mf">0.3</span><span class="p">,</span> <span class="n">time</span><span class="o">=</span><span class="mf">2.0</span><span class="p">,</span> <span class="n">init</span><span class="o">=</span><span class="mf">0.0</span><span class="p">)</span>
<span class="c1"># Pick a new value four times per second.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/randoms.html#pyo.Choice" title="pyo.lib.randoms.Choice"><span class="n">pick</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/randoms.html#pyo.Choice" title="pyo.lib.randoms.Choice"><span class="n">Choice</span></a><span class="p">([</span><span class="mi">200</span><span class="p">,</span> <span class="mi">250</span><span class="p">,</span> <span class="mi">300</span><span class="p">,</span> <span class="mi">350</span><span class="p">,</span> <span class="mi">400</span><span class="p">],</span> <span class="n">freq</span><span class="o">=</span><span class="mi">4</span><span class="p">)</span>
<span class="c1"># Print the chosen frequency</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/utils.html#pyo.Print" title="pyo.lib.utils.Print"><span class="n">pp</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/utils.html#pyo.Print" title="pyo.lib.utils.Print"><span class="n">Print</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/randoms.html#pyo.Choice" title="pyo.lib.randoms.Choice"><span class="n">pick</span></a><span class="p">,</span> <span class="n">method</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">message</span><span class="o">=</span><span class="s2">"Frequency"</span><span class="p">)</span>
<span class="c1"># Add an exponential portamento on an audio target and detune a second frequency.</span>
<span class="c1"># Sharp attack for rising notes and long release for falling notes.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/filters.html#pyo.Port" title="pyo.lib.filters.Port"><span class="n">freq</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/filters.html#pyo.Port" title="pyo.lib.filters.Port"><span class="n">Port</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/randoms.html#pyo.Choice" title="pyo.lib.randoms.Choice"><span class="n">pick</span></a><span class="p">,</span> <span class="n">risetime</span><span class="o">=</span><span class="mf">0.001</span><span class="p">,</span> <span class="n">falltime</span><span class="o">=</span><span class="mf">0.25</span><span class="p">,</span> <span class="n">mul</span><span class="o">=</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mf">1.005</span><span class="p">])</span>
<span class="c1"># Play with portamento times.</span>
<span class="n">freq</span><span class="o">.</span><span class="n">ctrl</span><span class="p">()</span>
<span class="c1"># Play a simple wave.</span>
<span class="n">sig</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.RCOsc" title="pyo.lib.generators.RCOsc"><span class="n">RCOsc</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/filters.html#pyo.Port" title="pyo.lib.filters.Port"><span class="n">freq</span></a><span class="p">,</span> <span class="n">sharp</span><span class="o">=</span><span class="mf">0.7</span><span class="p">,</span> <span class="n">mul</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.SigTo" title="pyo.lib.controls.SigTo"><span class="n">amp</span></a><span class="p">)</span><span class="o">.</span><span class="n">out</span><span class="p">()</span>
<span class="n">s</span><span class="o">.</span><span class="n">gui</span><span class="p">(</span><span class="nb">locals</span><span class="p">())</span>
</pre></div>
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