is the gain after decay.</li>
  <li><code>R</code> : Release time which is the length from note-off to
  the gain reaching to 0.</li>
  </ul>
  </dd>
  <dt>Gain</dt>
  <dd>
  <p>Master output gain.</p>
  </dd>
  </dl>
  <h4 id="lowpass"><a href="#lowpass" class="header-anchor"
  aria-hidden="true">Lowpass</a></h4>
  <p>This is a psuedo low-pass filter. It shifts to wavetable which
  contains less overtone to get low-passed output.</p>
  <p>Equation to get cutoff frequency is following.</p>
  <pre><code>cut 