While it is an amazing chart, the problem is that when you click on a point named "Rap" located in year 1972, a song from 1984 plays so I cannot hear what Rap sounded like in 1972 and how it evolved. I understand that there can be copyright issues, but one could put a link to Youtube or at least a track name. So it would be cool if the track played matched the year you click.

Edit: it seems you need to click on the rectangles rather than circles to choose the year.