 cutoff
  frequency.</p>
  <p><code>Attack</code> is introduced to prevent pop noise at note-on,
  when <code>Reset to Note On</code> is not checked. When lowpass cutoff
  in FDN is lowered, reducing <code>Attack</code> may cause pop noise.
  If the sound is dense at high frequency, like cymbal, it may be
  possible to set <code>Attack</code> to 0, because pop noise is
  unnoticeable.</p>
  </dd>
  <dt>Release [s]</dt>
  <dd>
  <p>Release time after note-off.</p>
  <p>Note that the value is not exact. It co