Took the player page and modified it to static HTML (rather than original PHP). Took me a while to figure out that the document.movie does not exist error was being thrown because an object element had bad attribute values, and it was nothing to do with the movie variable. Greg spotted that.
Once that was working, it was fairly straight forward to modify the javascript array and the javascript code (showEvents function in movie.js) that updates the UI to accommodate a third thread. Eventually that function will have to created on the fly based on the XML in the data file, but for purposes of demonstration we can use a hard-coded mockup.
Next feature to include will be min/max type controls for each thread in the GUI (more sophisticated version would also allow repositioning, but that can wait).