Apple Music's Launch, and the Effect of Streaming on the Pop Charts

Apple’s foray into the streaming music business launched with great fanfare today, though a plethora of streaming services like Spotify and Pandora and Google Play already exist. Apple Music has three offerings that you can’t get anywhere else yet—at least not legally: Taylor Swift’s 1989, Dr. Dre’s The Chronic, and an exclusive new single from Pharrell. As these services grow, and feature only certain songs and artists, it raises the question: does music exist if you can’t stream it? And how has streaming affected the Billboard charts?