Google has been known to do some interesting things with the data it collects from users, and here is yet another example of that. The company has found a way to visualize the data collected from Play Music users and display it on a Google Music Timeline. This timeline offers a visual representation on the growth and decline of certain genres of music (via Google Operating System Blog).
The graph displays a colored stripe for each genre of music. The thickness of each stripe represents the popularity of that genre in a given year. The data is collected from the music uploaded to Play Music by users. For instance, the Jazz stripe is thickest in the 1950s because many users have Jazz content released in that time period in their library.
The Music Timeline shows genres of music waxing and waning, based on how many Google Play Music users have an artist or album in their music library, and other data (such as album release dates). Each stripe on the graph represents a genre; the thickness of the stripe tells you roughly the popularity of music released in a given year in that genre. (For example, the “jazz” stripe is thick in the 1950s since many users’ libraries contain jazz albums released in the ’50s.) Click on the stripes to zoom into more specialized genres.