Starting today (Tuesday), fans who tweet #KATYNOW can unlock clues detailing two of the album’s tracks, including song titles, lyrics and video messages from Katy herself with additional surprises. Once the clues have been unlocked, Pepsi and MTV will stream samples of the two new songs on Saturday, Aug. 24, at Pepsi.MTV.com, where fans can then vote on which one they want to be released early by tweeting custom hashtags for their favorite track. The winning song will be announced Sunday night (Aug. 25), when Perry performs “Roar” at the close of the VMAs from an undisclosed location in Brooklyn to complement this year’s location at Barclays Center. The track will be released commercially Tuesday, Sept. 17. Additionally, Pepsi will give away downloads of “Roar” to any fan who registers for its Pepsi Experience Points rewards program.