The Google Research Blog has a really interesting visualization of changing trends in modern music. It’s based on the albums uploaded by uses into their Google Music accounts. This link is to the description of the data, the methodology and the caveats.
You can search by artist or album, or just glide along the timeline to see the changes.
And this link is to the actual visualization itself
Explore the history of Pop — and Punk, Jazz, and Folk — with the Music Timeline.