Google's Music Timeline lets you track the popularity of songs over the past 60 years. Want to know what was the feel-good hit of the summer, the exact moment in time that Justin Bieber will become passé or when Emo stepped out of the shadows and into the mainstream? Google?s Music Timeline has the answer. The timeline is a visual representation of data gathered from its Music Play users -- the songs they?ve been streaming, what?s in their library -- and combines it with other information such as music genre and album release dates, etc.

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