iTUNES has shifted the music business toward a singles-based model. While artists still release full albums and some, like Adele’s 21, sell very well, it’s also possible to produce a massive iTunes hit, like Carly Rae Jepsen’s “Call me Maybe,” before an album is even available (Jepsen’s full album sold modestly upon its later release). Even an established artist like Katy Perry initially saw singles from Teenage Dream outshine album sales; a parade of huge singles eventually drove the album back up the charts.