Forget Prince's "Purple Rules" demanding smartphone-free concerts, one group is actually encouraging fans to wave their handset in the air because it's part of the show. Electronic group Booka Shade recently performed a concert where the audience's phones played coordinated sound and lights via a custom app during songs, making them less of an annoyance and more an integral part of the performance.

"With so much opposition to using smartphones at gigs because of image and video rights infringement, we wanted to show how mobile technology can actually be used to make a performance even better," says band member Walter Merziger. The band collaborated on the project with Vodafone and an organization called Makelight Interactive. To take part phones need to have Makelight's app installed. They're then synced up at the show using a tone that also pinpoints where each handset is in the room based on how it hears the sound. The creative agency has made several light shows using phones for bands in the past (as have others), but this is the first time they've incorporated music into the mix.

Adding tunes meant the agency had to address new details like when and where sounds would play to achieve the perfect mix. When it came time for the technical rehearsal, they also ran into a huge issue: phones aren't loud enough on their own to make an impact at a live performance. The solution? The band handed out speaker accessories to make handsets 10 times as loud. The end result is a pretty epic show.