Felixyz

Here my (quick n’ dirty) workaround:
While nothing is showed when no wave is available, I’ve added some custom CSS:

.player {
   background-color: #f2f2f2;
   height: 80px !important;
}
wave {
   height: 20px !important;
   background-color: #bdbdbd}

canvas {
   height: 20px;}

canvas + wave {
   background-color: #9f9f9f;}

So my visitors can see the progress bar and use it to jump forward and backward.

HTH
Felix