Not sure whether a Keynote presentation via YouTube is valuable, but I am drawn to the idea that I can fix a lecture in time and archive it. I also mostly use Keynote to present media. Here’s one on visualizations for musical understanding (best viewed full screen and higher quality). I’ve also posted some copies of the Mozart visualization I use at archive.org: http://www.archive.org/details/MozartVisualizationsK.545ForClassroomTeachers