Katy Perry brought the 2013 iTunes Festival to an end with a bang. The American pop star took the stage at The Roundhouse in London to close the month-long concert series. Katy's set included four songs from her upcoming fourth studio album "Prism", due in stores October 22. Watch Katy perofrming her new music below!.
The John Mayer girlfriend opened the last 2013 iTunes Festival show with the this-week released iTunes countdown single, the 90's dance-pop "Walking On Air". Halfway the concert, it was time for urban Katy to make her appearance for a performance of "Dark Horse". Katy also treated her thousands of fans in the crowd, and the millions watching from their iOS devices online with a brand new, unheard song from "Prism", the beautiful ballad "By The Grace Of God". For the last song, Katy turned the volume up to "Roar"!....performing her latest global chart-topping hit.