nverts to filter cutoff
  frequency.</p>
  </dd>
  </dl>
  <h4 id="tuning"><a href="#tuning" class="header-anchor"
  aria-hidden="true">Tuning</a></h4>
  <dl>
  <dt>Octave, Semi, Milli</dt>
  <dd>
  <p>Changes master pitch.</p>
  <p><code>Milli</code> is 1/1000 of semitone or 1/10 cent.</p>
  </dd>
  <dt>ET, A4 [Hz]</dt>
  <dd>
  <p>Changes tuning.</p>
  <p><code>ET</code> stands for equal temperament. Note that when
  <code>ET</code> is less than 12, some notes becomes silent due to
  frequency becomes too