ts impact to the same object again and again, do not
  check <code>Retrigger</code>.</p>
  </dd>
  <dt>Wave Interp.</dt>
  <dd>
  <p>LFO wave form interpolation method.</p>
  <ul>
  <li><code>Step</code>: Holding.</li>
  <li><code>Linear</code>: Linear interpolation.</li>
  <li><code>PCHIP</code>: Monotonic cubic interpolation.</li>
  </ul>
  <p><code>Step</code> makes LFO to act like a sequencer.
  <code>Linear</code> sounds similar to <code>PCHIP</code>, and the
  computation cost is lower. <code>PCHIP</c