 4: Parallel composition</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-5-controlling-the-volume" class="nav-link">Example 5: Controlling the volume</a>
              <ul class="nav flex-column">
              </ul>
            </li>
            <li class="nav-item" data-level="3"><a href="#example-6-controlling-the-volume-with-a-slider" class="nav-link">Example 6: Controlling the volume with a slider</a>