A new "Hamilton" album features some of the biggest stars in pop music. The 23-track "Hamilton Mixtape," which comes out on Friday, features covers by artists like Kelly Clarkson, Usher, Nas, Alicia Keys, John Legend, and Sia. The Broadway sensation already has a bestselling cast album. The mixtape came as a surprise with a special four song performance on Thursday at the Richard Rodgers Theater. The theater was packed with fans who won seats through an online lottery.