We've all seen those musical instrument apps for smartphones. There are ones that emulate functions of drums, keyboard, guitars, even microphones. Heck, you could even put together a band with just iPhones and instrument apps.
In fact, the band Atomic Tom decided to do just that and performed on the B line of the New York subway.
This video has since gone viral, much to the band's pleasure. It doesn't appear to be a marketing stunt by Apple, but it might as well have been as the videos were shot with iPhone 4's.