The 'Do It Like A Dude' singer will perform at Camden's Roundhouse venue on July 15.
"iTunes is where the music happens," she told Metro. "Let's hope I can bring some of that magic to the stage."
Acts already confirmed for the month-long London event include Duran Duran, Beady Eye and Adele.
Tickets for the shows are free and can be won by entering a prize draw on the official festival website.