educed. When
  <code>Harmonic HP</code> is 0, highpass filter is bypassed.</p>
  <p>Following shows the computation of <code>Harmonic HP</code>.</p>
  <pre><code>for index in [0, harmonicHighpass) {
  sourceSpectrum[index].amp *= index / harmonicHighpass;
}</code></pre>
  </dd>
  <dt>Blur</dt>
  <dd>
  <p>Coefficient of lowpass filter which applies to source spectrum
  amplitude.</p>
  <p>Reducing <code>Blur</code> diffuses frequency amplitude to adjacent
  indices. It means that the resulting sound becomes